Multilayered barrier structures

ABSTRACT

Multilayered barrier structures comprising a gas barrier layer of a non-chlorine containing organic polymer which is substantially impermeable to oxygen gas and a moisture barrier layer of a mesophase propylene-based material are provided. These structures are environmentally compatible and radiation resistant, and exhibit one or more additional properties, including gas barrier properties, moisture barrier properties, toughness, heat sealability, softness, and quietness during wrinkling. Also provided are methods of preparing and using such multilayered barrier structures, and articles, such as films, pouches, and tubings, formed from these structures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.07/810,001, filed Dec. 18, 1991 now abandoned.

FIELD OF THE INVENTION

This invention relates to multilayered barrier structures exhibiting oneor more properties, including gas barrier properties, moisture barrierproperties, radiation resistance, toughness, heat sealability, quietnessduring wrinkling, and environmental compatibility. The invention alsorelates to methods of preparing and using such multilayered barrierstructures, as well as to articles formed from such structures.

BACKGROUND OF THE INVENTION

Multilayered structures which are both substantially impervious to gasesand/or moisture are well known in the medical and food packagingindustries. However, current structures suffer from a variety ofproblems, including environmental incompatibility, rapid deteriorationafter exposure to sterilizing radiation, lack of toughness, ineffectiveheat sealability, and an embarrassing tendency for personal carearticles manufactured from these structures, such as ostomy pouches, tomake noise due to wrinkling during use.

Currently, poly(vinylidine chloride) (PVDC) is used as one of thematerials of choice for the gas barrier component of barrier films. Forostomy applications, a film of PVDC sandwiched between opposing layersof low density polyethylene (LDPE) is widely used, with PVDC functioningas the gas barrier, and LDPE as the moisture barrier. Also, polyvinylchloride (PVC) can be used in the moisture barrier layer, or otherlayers, of such a structure. However, disposal of thesechlorine-containing materials presents a number of environmentalconcerns, especially relating to incineration of these materials afteruse in hospitals or otherwise.

Both PVDC and PVC are viewed as hazardous to the environment and topersonal health. Incineration of PVDC/PVC results in release ofhydrochloric acid (HCl), providing the major portion of HCl inincinerator flue gases. Also, PVDC/PVC is suspected of contributing topolychlorinated dibenzodioxin and furan toxins formed duringincineration. Levels of these toxins are up to three times greater inmedical infectious waste as compared to municipal waste streams. Seee.g., Staff Report, "Proposed Dioxius Control Measure for Medical WasteIncinerators", State of California, Air Resources Board, StationarySource Division, pp. 1-40 (May 25, 1990); Medical Waste PolicyCommittee, "Perspectives on Medical Waste", A Report of the Nelson ARockefeller Institute of Government, State University of New York (June,1989). In addition to incineration concerns, exposure todi-2-ethylhexylphthalate (DEHP), a common plasticizer utilized with PVDCand PVC, may present a number of health-related concerns, includingreduced blood platelet efficacy, and potential links to liver cancer.See e.g., Allwood, M. C., "The Release of phthalate ester plasticizerfrom intravenous administration sets into fat emulsion", 29International Journal of Pharmacology, 233-6 (1986).

Examples of barrier structures incorporating such hazardouschlorine-containing materials can be found in various U.S. Patents, suchas U.S. Pat. No. 3,524,795, which discloses a layered packaging materialwith a gas barrier layer comprised of various vinyl chlorine-containingpolymers, and U.S. Pat. No. 4,786,561, which discloses a heat-shrinkablebarrier film of an oriented polyolefin film coated on one side with avinylidene chloride copolymer. In addition, numerous other patentdocuments, including U.S. Pat. Nos. 5,009,648, 4,983,171, 4,906,495,4,880,592, 4,826,493; British Patent Application No. GB 2138431; andEuropean Patent Application No. EP 0433060; all disclose multilayeredfilms which utilize chlorine-containing polymers for the construction ofostomy pouches and other personal care articles.

Crystalline polypropylene provides excellent protection from moistureand is often a material of choice for barrier structures, and formedical articles manufactured therefrom. In addition, crystallinepolypropylene exhibits a number of other desirable properties, such asnon-toxicity, chemical resistance and inertness to drugs and liquidmedia used with drugs, as well as its low cost and ease of processing bymeans of extrusion, molding, and the like. However, a disadvantage ofcrystalline polypropylene is its inherent inability to be heat sealed toother materials. Thus, medical articles, such as barrier structures, orpackaging for medical articles, often cannot be effectively heat-sealedin the manufacture and/or assembly of the components of the article.Furthermore, similar problems may also occur in the packaging ofpharmaceuticals or medical articles in an effort to protect them fromundesired exposure to environmental contaminants, including pathogenicorganisms.

Even after manufacture and assembly, such barrier structures and/ormedical articles often require additional protection beyond secure heatsealing and package processing. Accordingly, such materials should besterilized at the time of production, and thereafter maintained in asterile condition during storage. While not all structures or articlesrequire sterilization prior to usage, structural components which areresistant to radiation are more versatile for uses in medical articlesand packaging than components unable to maintain structural integrityafter irradiation. Thus, the most desirable material for a barrierstructure, medical article, or the packaging formed therefrom, is onewhich possesses resistance to the structurally demanding forms ofsterilization, such as by gamma or electron-beam radiation, even ifcurrent usages of the structure or articles do not require suchsterilization.

A preferred method of sterilization uses gamma radiation, such asradioactive cobalt 60, since it can be performed on packages sealed byheat or other methods, insuring total and reliable sterility of thecontents. In addition, electron beam radiation can also be utilized tosterilize barrier structures, medical articles, and/or their packagingmaterials.

Unfortunately, a further disadvantage of crystalline polypropylene isthat gamma-irradiation or electron-beam irradiation causes degradationof its structural integrity (e.g., causing embrittlement, discoloration,and thermal sensitivity). Thus, barrier films incorporating crystallinepolypropylene in moisture barrier layers, or other layers, and thearticles or packaging materials formed therefrom, are incapable ofmaintaining their structural integrity for a useful period of time afterexposure to ionizing radiation.

Examples of barrier structures and/or the articles formed from thesestructures which incorporate crystalline polypropylene are shown innumerous U.S. and foreign patents, including U.S. Pat. Nos. 4,217,161and 4,511,610, which disclose multilayered plastic vessels orcontainers, and processes for making such containers. The filmscomprising these vessels or containers include an inner gas barrierlayer and outer moisture barrier layers of a crystalline polyolefin,preferably crystalline polypropylene or crystallinepolypropylene/ethylene copolymers.

U.S. Pat. Nos. 4,239,826 and 4,254,169, both disclose multi-layerbarrier films with a core gas barrier layer of a vinyl alcohol polymeror copolymer between opposing layers of a polyolefin blended with achemically-modified polyolefin containing functional groups addedthereto. Examples of chemically-modified polyolefins include vinylacetate-vinyl alcohol copolymers, vinyl alcohol-ethylene vinyl acetateterpolymers, or high density polyethylene with an unsaturated fused-ringcarboxylic acid grafted thereto. In addition, the films can containadditional outer layers overlying the modified polyolefin layers ofpolyolefin polymers or copolymers, such as high, medium and low densitypolyethylene, polypropylene, ethylene vinyl acetate copolymers, ethyleneacrylic acid copolymers, nylons, or blends thereof.

Other exemplary patents include, Japanese Patent Application No. Sho60[1085]-217190, published Apr. 6, 1987, which discloses a plasticlaminate comprised of a polyvinyl alcohol gas barrier layer, with aplastic, olefin-containing, vapor barrier layer laminated thereto. Also,U.S. Pat. No. 4,064,296 discloses a heat shrinkable, multilayer filmhaving a gas barrier layer and outer moisture barrier layers of orientedolefin polymers, which have been crosslinked through exposure toionizing radiation. In addition, U.S. Pat. No. 4,407,897 discloses amulti-layer polymeric structure with a drying agent incorporatedtherein, and with outer moisture barrier layers of polymers such aspolyethylene, polypropylene, or blends thereof.

Attempts have been made to overcome degradation problems associated withcrystalline polypropylene. For example, mesomorphous polypropylene, asdescribed in U.S. Pat. No. 4,931,230, and articles manufactured frommesomorphous polypropylene, such as described in U.S. Pat. No.4,950,549, provide resistance to sterilizing irradiation. By controllingthe method of preparing mesomorphous polypropylene, through thequenching of such polypropylene after hot-melt extrusion, the materialor articles formed therefrom substantially maintain their structuralintegrity after exposure to ionizing radiation at dosages sufficient todegrade crystalline polypropylene.

Unfortunately, single-layer packaging films and the like made fromcrystalline polypropylene, or even mesomorphous polypropylene, aresusceptible to tearing and puncturing which would disrupt the structuralintegrity of a manufactured component or packaging film after assembly.Thus, the usefulness of a sterilized medical article would becompromised by a puncture or tear in a polypropylene package. Inaddition, single-layer crystalline polypropylene cannot be effectivelyheat sealed against another material. Furthermore, even thoughmesomorphous polypropylene provides better heat sealability thancrystalline polypropylene, in certain instances it still cannot providea sufficient heat seal to manufacture a multicomponent medical article,or to provide an effective radiation-sterilized package.

In an effort to overcome these deficiencies, polymer blends ofmesomorphous polypropylene and a polymer compatible with suchpolypropylene, as described in European Patent Application No. 0 405 793(assigned to the same assignee as for this application) have beendeveloped. These polymer blends exhibit enhanced physical properties,such as heat sealability and tear strength, while maintaining theradiation resistance associated with mesomorphous polypropylene.

Though mesomorphous polypropylene, or blends thereof, may be radiationresistant, the materials comprising the gas barrier layer of barrierfilms typically are not. For example, as described in Evalca TechnicalBulletin No. 140 (available from Evalca Co., of EVAL America, located inLyle, Ill.), typical gas barrier polymers, such as ethylene vinylalcohol (EVOH) rapidly degrade after exposure to ionizing radiation.Furthermore, the polymeric adhesive layers often employed in suchbarrier films would also be expected to rapidly degrade after exposureto ionizing radiation.

To date, no barrier film exists which combines radiation resistance withenvironmental compatibility. Furthermore, there are no such barrierfilms which likewise exhibit one or more good packaging or componentarticle properties, such as heat sealability, toughness, softness, andquietness.

SUMMARY OF THE INVENTION

There is a need for an environmentally compatible multilayer barrierfilm capable of maintaining its structural integrity for a useful periodof time after exposure to ionizing radiation at a dosage sufficient tosterilize such a film, as well as for articles manufactured therefrom.Preferably such a film would also be tough, heat sealable, soft and/orquiet.

The present invention overcomes the deficiencies of previous barrierfilms and related articles by providing multilayered barrier structureswhich are both environmentally compatible and resistant to sterilizationvia ionizing radiation, and which display barrier properties to gasessuch as O₂, CO₂, H₂ S, and odors, as well as to moisture. In addition,these multilayered barrier films exhibit one or more other desirableproperties, including superior toughness, heat sealability, quietnessand softness.

In particular, the present invention provides a multilayered barrierstructure having a gas barrier layer of a non-chlorine containingorganic polymer which is substantially impermeable to oxygen gas, and amoisture barrier layer of a mesophase propylene-based material.Preferably, the gas barrier layer exhibits a permeability to oxygen gasof less than 100 cc/m² /d-atm at 25° C. and 0% relative humidity. Sincethe multilayered barrier structures are chlorine-free, they can bedisposed of via incineration without presenting a threat to theenvironment or personal safety.

The mesophase propylene-based materials of the moisture barrier layercan comprise mesomorphous polypropylene, mesopolymer blends, and/ormesocopolymers. In this regard, the present invention can providemultilayered barrier structures wherein the moisture barrier layercomprises mesomorphous polypropylene homopolymer, or a mesopolymer blendof mesomorphous polypropylene and at least one second polymer.Preferably, the second polymer is a compatible polymer whichsynergistically increases one or more of the physical properties, suchas toughness, heat sealability, softness, and/or quietness, of themultilayered barrier structure.

In another aspect, the present invention also can provide multilayeredbarrier structures wherein the moisture barrier layer comprises amesocopolymer. Like the mesomorphous polypropylene and mesopolymerblends of the present invention, mesocopolymers can provide moisturebarrier layer(s) of the multilayered barrier structure of the presentinvention that are tougher, softer, quieter, and/or more heat sealablethan a corresponding copolymer with crystalline propylene therein.

The present invention also provides a method for preparing amultilayered barrier structure by coextruding a propylene-based materialalong with a non-chlorine containing organic polymer which issubstantially impermeable to oxygen gas, to form a multilayeredextrudate, and quenching the extrudate immediately after extruding toprovide a multilayered barrier structure with a core layer of thenonchlorine containing organic polymer and at least one layer of amesophase propylene-based material adjacent thereto.

In addition, the present invention provides a multilayered barrierstructure for use as a barrier film. Specifically, a method ofinterposing a multilayered barrier film, including a gas barrier layerof a non-chlorine containing organic polymer, and at least one moisturebarrier layer of a mesophase propylene-based material, between aprotected environment and an external environment, such that gases andmoisture cannot substantially pass therethrough, is provided.

Furthermore, the present invention also provides various articles formedfrom the multilayered barrier structures of the present invention,including, ostomy pouches, incontinence products, tapes, tubings,transdermal drug-delivery patches and packaging for medical and/or foodproducts. Although the desired applications for these multilayeredbarrier structures are in a film form, the multilayered constructionscould also be used for applications requiring rigid and semi-rigidstructures, such as for medical containers, as well as for flexiblestructures, such as tubings and tapes. Also, the present invention canprovide articles with surfaces that are modified using irradiation. Foran additional appreciation of the scope of the present invention, a moredetailed description of the invention follows, with reference to thedrawings.

Definitions

For the purposes of this invention the definition of "polymer" includesa homopolymer, a copolymer, or an oligomer, as well as any mixtures orblends of one or more homopolymers, and/or one or more copolymers,and/or one or more oligomers.

The term "copolymer" refers to a polymeric material produced by thepolymerization of two or more dissimilar monomers, either with orwithout another functional group, such as maleic anhydride, graftedthereto, as well as to a homopolymer with a functional group graftedthereto. Thus, the term "copolymer" includes, without limitation, randomcopolymers, block copolymers, sequential copolymers, and graftcopolymers.

"Propylene-based material" refers to propylene monomer, or polypropylenepolymer.

The term "moiety" refers to any substance which can be combined with apropylene-based material to form a copolymer, and includes, withoutlimitation, a monomer, a polymer, or a molecule.

"Mesophase propylene-based material", refers to a propylene-basedmaterial, in the ordered, mesophase form, which is neither amorphous,nor so ordered as to constitute the isotactic I crystalline form (e.g.,crystalline polypropylene) as described by G. Natta et al., "Structureand Properties of Isotactic Polypropylene", Del Nuovo Cimento, Suppl A1,Vol XV, Series X, No. 1, 1960, pp. 40-51, the disclosure of which isherein incorporated by reference. A mesophase propylene-based materialis formed by quenching a propylene-based material from the melt state,as defined below, and includes, without limitation, mesomorphouspolypropylene, mesopolymer blends, and/or mesocopolymers, as those termsare defined below.

"Quenching", refers the process of immediately and rapidly coolingpropylene-based material from the melt state such that mesophasepropylene-based material is obtained.

As used herein, "a non-chlorine containing organic polymer which issubstantially impermeable to oxygen gas" refers to polymeric materialswhich are essentially free from chlorine, and which have oxygentransmission rates of less than about 150 cc/m² /day-atmosphere at 25°C. and 0% relative humidity.

"Olefin polymers" or "polyolefins", refers to polymers of theunsaturated hydrocarbons of the general formula C_(n) H_(2n), includingcopolymers of olefins with other monomers such as ethylene with vinylacetate.

"Mesomorphous polypropylene" (mPP) refers to the polypropylenehomopolymer in the mesophase form.

The term "mesopolymer blend" refers to a mixture of mesomorphouspolypropylene with at least one additional polymer (hereinafter a"second polymer").

The term "mesocopolymer" refers to a copolymer of a propylene-basedmaterial and a discernable amount of at least one moiety that isquenched from the melt state to form a copolymer in the mesophase form.

The "Rule of Mixtures" refers to a means for determining thehypothetical values for a given physical property of a blend of two ormore polymers. The hypothetical value represents the summation of theproportional contribution of the actual values of the physical propertyfrom each of the constituent polymers, based on the weight percents ofthe constituent polymers incorporated into the blend. Under the "Rule ofMixtures", the value for a given physical property (property "X") of ablend of two polymers (polymers A & B) can be calculated according tothe following formula: Hypothetical value of property "X" for a blend ofpolymers A & B=(Weight percent of polymer A in the blend)×(actual valueof property "X" for polymer A)+(Weight percent of polymer B in the blendB)×(actual value of property "X" for polymer B).

A "compatible polymer" refers to any second polymer which when combinedwith mesomorphous polypropylene, forms a mesopolymer blend wherein atleast one weight fraction of the mesopolymer blend has a more desirablephysical property than would be expected under the Rule of Mixtures.

A "tempering additive", refers to any polymer, which when combined intoone or more layers of a multilayered barrier structure according to thepresent invention, functions to modify the film properties, such asYoung's modulus, fracture strain, and/or the frequency in Hertz (Hz) ofsound emitted from a multilayered barrier structure when wrinkled, suchthat a soft, tough, and/or quiet multilayered barrier structure isobtained.

The "structural integrity" of a multilayered structure is measured bythe percent elongation to break of that structure. With respect toradiation resistance of such structures, percent elongation to break isused to measure the extent of degradation or embrittlement of thesestructures after irradiation. A substantially constant percentelongation at break over several months after irradiation is indicativeof substantial maintenance of structural integrity of a multilayeredstructure over that period after irradiation.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be further illustrated by reference to theaccompanying Drawing wherein:

FIG. 1 is a cross-sectional illustration of a first embodiment of amultilayered barrier structure according to the present invention;

FIG. 2 is a cross-sectional illustration of a second embodiment of amultilayered barrier structure according to the present invention;

FIG. 3 is the wide-angle x-ray diffraction pattern of mesomorphouspolypropylene;

FIG. 4 is the wide-angle x-ray diffraction pattern of an 80/20mesopolymer blend by weight of mesomorphous polypropylene withpolybutylene;

FIG. 5 is the wide-angle x-ray diffraction pattern of a 50/50mesopolymer blend by weight of mesomorphous polypropylene withpolybutylene;

FIG. 6 is the wide-angle x-ray diffraction pattern of a 20/80mesopolymer blend by weight of mesomorphous polypropylene withpolybutylene;

FIG. 7 is the wide-angle x-ray diffraction pattern of polybutylene;

FIG. 8 is the wide-angle x-ray diffraction pattern of a 50/50mesopolymer blend by weight of mesomorphous polypropylene withpolybutylene;

FIG. 9 is the wide-angle x-ray diffraction pattern of crystallinepolypropylene;

FIG. 10 is the wide-angle x-ray diffraction pattern of an 80/20 blend byweight of crystalline polypropylene with polybutylene;

FIG. 11 is the wide-angle x-ray diffraction pattern of a 50/50 blend byweight of crystalline polypropylene with polybutylene;

FIG. 12 is another wide-angle x-ray diffraction pattern of a 50/50 blendby weight of crystalline polypropylene with polybutylene;

FIG. 13 is a graph comparing Young's modulus of the multilayered barrierstructures of Examples 1-4 and Comparison Example 5 (line A) withhypothetical linear values for Examples 1-4 and Comparison Example 5(line B);

FIG. 14 is a graph comparing the yield stress of the multilayeredbarrier structures of Examples 1-4 and Comparison Example 5 (line A)with hypothetical linear values for Examples 1-4 and Comparison Example5 (line B);

FIG. 15 is a graph comparing Young's modulus of the multilayered barrierstructures of Examples 56-60 (line A) with hypothetical linear valuesfor Examples 56-60 (line B);

FIG. 16 is a graph comparing Young's modulus of the multilayered barrierstructures of Examples 60-64 (line A) with hypothetical linear valuesfor Examples 60-64 (line B);

FIG. 17 is a graph comparing the fracture strain of the multilayeredbarrier structures of Examples 51 and 58-61 (line A) with hypotheticallinear values for Examples 51 and 58-61 (line B);

FIG. 18 is a graph comparing the radical decay as measured in normalizedradical peak height in spins/gram as a function of elapsed time in hoursfor the multilayer barrier structures of Example 46 (line A) andComparison Example 52 (line B) after exposure to a 50 kGy dosage ofelectron beam radiation;

FIG. 19 is a graph comparing the radical decay as measured in normalizedradical peak height in spins/gram as a function of elapsed time in hoursfor the multilayered barrier structures of Example 47 (line A) andComparison Example 53 (line B) after exposure to a 50 kGy dosage ofelectron beam radiation;

FIG. 20 is a graph comparing the radical decay as measured in normalizedradical peak height in spins/gram as a function of elapsed time in hoursfor the multilayered barrier structures of Examples 48 and 50 (line A)and Comparison Examples 54 (line B) and 55 (line C) after exposure to a50 kGy dosage of electron beam radiation;

FIG. 21 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Example 1;

FIG. 22 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Comparison Example 7;

FIG. 23 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Example 2;

FIG. 24 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Comparison Example 8;

FIG. 25 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Example 6;

FIG. 26 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Comparison Example 9;

FIG. 27 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Example 57;

FIG. 28 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Comparison Example 73;

FIG. 29 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Example 63;

FIG. 30 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Comparison Example 78;

FIG. 31 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Example 64;

FIG. 32 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Example 79;

FIG. 33 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Example 66;

FIG. 34 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Comparison Example 81;

FIG. 35 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Example 69; and

FIG. 36 is a graph of the noise spectra intensity (V) versus frequency(Hz) of the multilayered barrier structure of Comparison Example 84.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Multilayered Barrier Structures

FIGS. 1 and 2 show cross-sectional views of two embodiments ofmultilayered barrier structures 10,30 according to the presentinvention. FIG. 1 shows a first embodiment. The multilayered barrierstructure 10 comprises a gas barrier layer 12, with a moisture barrierlayer 14 contacting opposing sides 16,18 of the gas barrier layer 12.While it is preferable that the multilayered barrier structure 10include moisture barrier layers 14 on each of the opposing sides 16,18of the gas barrier layer 12, it will be appreciated that in certainapplications, that the multilayered barrier structure 10 need onlyinclude a single moisture barrier layer 14 on one of the opposing sides16,18 of the gas barrier layer 12.

FIG. 2 shows a second embodiment of a multilayered barrier structure 30having a gas barrier layer 32 and opposing moisture barrier layers 34proximate the opposing sides 36,38 of the gas barrier layer 32. Inaddition, this embodiment includes an optional adhesive layer 40contacting the opposing sides 36,38 of the gas barrier layer 32, inbetween the gas barrier layer 32 and moisture barrier layers 34. Thus,the second embodiment contemplates a five layered barrier structure,comprising a central gas barrier layer 32, with adhesive layers 40 oneach of the opposing sides 36,38 of the gas barrier layer 32, and amoisture barrier layer 34 contacted with each of the two adhesive layers40. However, it will be appreciated that any multilayered barrierstructure 10,30 with two or more layers, which includes at least one gasbarrier layer 12,32, and at least one moisture barrier layer 14,34, isconsidered to fall within the scope of the present invention.

Throughout the remaining description of the embodiments of theinvention, primary reference will be had to the embodiment illustratedin FIG. 1, unless otherwise indicated. However, it will be appreciatedthat this description also applies to the embodiment illustrated in FIG.2.

Gas Barrier Layer

The gas barrier layer 12 of the multilayered structure 10 is comprisedof a non-chlorine containing organic polymer which is substantiallyimpermeable to oxygen gas. Preferably, the non-chlorine containingorganic polymer exhibits a permeability to oxygen (O₂) gas of less than100 cc/m² /day-atmosphere (hereinafter expressed as "cc/m² /d-atm"),more preferably less than 30 cc/m² /d-atm, and most preferably less than5 cc-25μ/m² /d-atm, where the permeability measurements are taken at 25°C. and zero percent (0%) relative humidity. It will also be appreciatedthat the O₂ permeability measurements are expressed for a multilayeredbarrier structure with a gas barrier layer thickness of 25μ (microns).Accordingly, appropriate adjustment of the permeability values must bemade, depending upon the thickness of the gas barrier employed in astructure, as well as the number of gas barrier layers utilized therein.In either case, the values should be normalized to a total gas barrierlayer thickness of 25μ. All values were normalized to standard gasbarrier layer thickness of 25μ by multiplying the oxygen transmissionrate value by the ratio of barrier layer thickness to 25μ. In additionto substantial impermeability to O₂ gas, it will further be appreciatedthat the gas barrier layer 12 also exhibits barrier properties to CO₂,N₂ and H₂ S gases, as well as to other gases and odors.

Nonlimiting examples of non-chlorine containing organic polymers inaccordance with the present invention include vinyl alcohol containingpolymers, such as ethylene vinyl alcohol copolymer (EVOH) and polyvinylalcohol (PVOH), polyacrylonitrile, polystyrene, polyester, and nylon,either alone, or blended with each other, or another polymer.Preferably, the non-chlorine containing organic polymer comprises avinyl alcohol containing polymer such as EVOH or PVOH, with EVOH beingparticularly preferred. Also, the gas barrier layer 12 should preferablybe comprised of substantially pure EVOH, most preferably comprising 99%or more EVOH. However, it also within the scope of the present inventionto utilize blends of EVOH with other polymers, such as ethylene vinylacetate copolymer.

Moisture Barrier Layer

The barrier properties of the gas barrier layer 12 of the multilayeredbarrier structure 10 are reduced in high moisture conditions.Accordingly, a moisture barrier layer 14 in accordance with theprinciples of the present invention is contacted with at least one side16,18 of the gas barrier layer 12 to provide moisture protection for thegas barrier layer 12.

The moisture barrier layer 14 is comprised of a mesophasepropylene-based material, such as mesomorphous polypropylene,mesopolymer blends, and/or mesocopolymers. Incorporation of the moisturebarrier layer 14 comprised of mesomorphous polypropylene homopolymer,mesopolymer blends containing mesomorphous polypropylene, and/ormesocopolymers, into the multilayered barrier structure 10 according tothe present invention unexpectedly enhances the overall properties ofthe multilayered barrier structure 10. In addition, by combiningmesomorphous polypropylene with selected second polymers (i.e.,compatible polymers) according to the present invention, mesopolymerblends may be obtained which exhibit enhanced properties over what wouldbe expected of such blends under the Rule of Mixtures, as defined above.Furthermore, mesocopolymers used in the moisture barrier layer 14 alsoexhibit enhanced properties over that of copolymers incorporating thesame moieties with propylene in a crystalline form. When thesemesopolymer blends and/or mesocopolymers are incorporated into themultilayered barrier structure 10 via the moisture barrier layers 14,the overall properties of the multilayered barrier structure 10 islikewise enhanced.

For example, as described in European Patent Application No. 0 405 793,published Jan. 2, 1991, the disclosure of which is herein incorporatedby reference, polymer blends of mesomorphous polypropylene and a"compatible" polymer exhibit increased resistance to the degradingeffects of ionizing radiation, including gamma and electron-beamradiation, which are typically employed to sterilize packaging materialsand medical articles. Furthermore, the mesopolymer blends may exhibitother desirable properties attributable to the compatible polymers, asthat term is defined herein, such as increased toughness, heatsealability, softness, and quietness, depending upon the particularcompatible polymer combined in the mesopolymer blend.

Surprisingly, utilization of mesomorphous polypropylene, mesocopolymers,and/or mesopolymer blends, such as those disclosed in European PatentApplication No. 0 405 793, in the moisture barrier layer(s) 14unexpectedly imparts increased radiation resistance to the overallmultilayered barrier structure 10, including the gas barrier layer 12and optional adhesive layers 40, and enhances other overall propertiesof the multilayered barrier structure 10 of the present invention, suchas toughness, heat sealability, softness and/or quietness. See also,Applicants' copending and co-filed U.S. patent applications, Ser. Nos.07/809,956 (Rolando et al.) and 07/809,959 (Wilfong et al.). Also, themesopolymer blends employed in the present invention need not be limitedto combinations of mesomorphous polypropylene with compatible polymers,as that term is defined herein. Instead, any of one or more secondpolymers which can be combined with polypropylene, melt extruded, andquenched, such that the resulting mesopolymer blend includesmesomorphous polypropylene is considered to be within the scope of thepresent invention. However, it is preferable that the second polymerenhance the physical properties or characteristics of the mesopolymerblend when combined with mesomorphous polypropylene.

Nonlimiting examples of second polymers include polybutylene (PB);polybutylene copolymers; atactic polypropylene resins available fromHimont USA Inc., of Wilmington, Del.; polypropylene-ethylene copolymers;ethylene vinyl acetate copolymer (EVA); acid modified EVA; anhydridemodified EVA; acid/anhydride modified EVA; ethylene acrylic acidcopolymer (EAA); acid modified ethylene acrylate; anhydride modifiedethylene acrylate; poly(4-methyl pentene); polyethylene, polyethylenecopolymers, low density polyethylene (LDPE), linear low densitypolyethylene (LLDPE), high density polyethylene (HDPE); andacid/anhydride modified polypropylenes. Particularly preferred secondpolymers include polybutylene, EVA, and EAA. It will be appreciated thatthis list of second polymers is not exhaustive of second polymers whichcan be combined with mesomorphous polypropylene to form the mesopolymerblends utilized in certain embodiments of the moisture barrier layer(s)14 of the multilayered barrier structure 10 of the present invention.See, e.g., Applicants' copending and co-filed U.S. patent application,Ser. No. 07/809,959 now abandoned, assigned to the Assignee of thepresent invention, the disclosure of which is herein incorporated byreference.

As noted above, the moisture barrier layer(s) 14 may be formed solely ofmesomorphous polypropylene. However, in other embodiments, a moisturebarrier layer 14 comprised of a mesopolymer blend of mesomorphouspolypropylene and one or more second polymer will be preferred. In suchembodiments, the optimum weight fraction of the second polymer with themesomorphous polypropylene depends upon the intended use and desiredproperties for the moisture barrier layer 14, and the final multilayeredbarrier structure 10 formed therefrom. Generally, when a mesopolymerblend is to be employed, it is desirable to add as much second polymeras possible to provide the needed strength, heat sealability, softness,quietness, and/or other desirable properties, without compromising theradiation resistance provided by the mesomorphous polypropylene of themesopolymer blend.

However, when utilizing a mesopolymer blend, it is within the scope ofthis invention to add a discernibly minimal amount of the second polymerto the mesomorphous polypropylene to provide a mesopolymer blend, andresulting moisture barrier layer 14, quenched to preserve themesomorphous polypropylene, having excellent resistance to sterilizingradiation, and better physical properties, such as heat sealability andtoughness, than when the mesomorphous polypropylene homopolymer isutilized alone.

Optionally, as little as one percent (1%) by weight of the secondpolymer to the weight of the mesopolymer blend, quenched to preservemesomorphous polypropylene, can form an acceptable mesopolymer blendutilized to form the moisture barrier layer(s) 14, and resultingmultilayered structure 10, of the present invention. Such a mesopolymerblend can prove acceptable for certain medical applications requiringsuperior radiation resistance, and can also exhibit other desirablebarrier and/or packaging properties.

It is also within the scope of the present invention to add adiscernibly minimal amount of polypropylene to the second polymer toprovide a mesopolymer blend, quenched to preserve mesomorphouspolypropylene, wherein the moisture barrier layer 14, and resultingmultilayered barrier structure 10, exhibits excellent barrier and/orpackaging properties, and acceptable radiation resistance. Thus, when amesopolymer blend is called for, optionally, as much as ninety-ninepercent (99%) by weight of the second polymer to the weight of themesopolymer blend, may form an acceptable mesopolymer blend according tothe present invention.

It is desirable that the weight fraction range of the second polymer isfrom about five percent (5%) to about ninety-five percent (95%) byweight, and more desirably from about ten percent (10%) to about ninetypercent (90%) by weight of the mesopolymer blend.

Preferably, when it is desirable to balance the best properties of themesomorphous polypropylene and the second polymer in the mesopolymerblend, the weight fraction of the second polymer should range from abouttwenty percent (20%) to about eighty percent (80%) by weight, morepreferably from about twenty-five percent (25%) to about seventy-fivepercent (75%) by weight of the mesopolymer blend, and most preferablyfrom about forty percent (40%) to about sixty percent (60%) by weight ofthe mesopolymer blend.

Previously, it was unknown for copolymers of propylene-based materialswith other moieties to form a mesophase form upon quenching. However, ithas now been surprisingly discovered that these mesocopolymers providemany, if not all, of the same advantages as mesomorphous polypropyleneand mesopolymer blends, such as increased resistance to ionizingradiation, toughness, softness, heat sealability and/or quietness.Accordingly, mesocopolymers can be used to form the moisture barrierlayer(s) 14, and/or optional adhesive layer(s) 40, of the multilayeredbarrier structure 10 of the present invention.

Any moiety, or combination of moieties, can be used in conjunction witha propylene-based material to form the mesocopolymers according to thepresent invention. See, e.g., Applicants' copending and cofiled U.S.patent application, Ser. No. 07/809,956, assigned to the Assignee of thepresent invention, the disclosure of which is herein incorporated byreference. For example, the propylene-based material can comprisepropylene monomer and the moiety of a different monomer other thanpropylene, such as ethylene or butylene, that when polymerized, meltextruded, and quenched, from a mesocopolymer within the scope of thepresent invention.

The mesocopolymers according to the present invention generally fallwithin three classes. The first class of copolymer comprises amesocopolymer wherein the other moiety comprises a monomer, such asethylene or butylene, that is inserted between propylene monomers in acopolymer chain. Accordingly, class one copolymers according to thepresent invention include, without limitation, random, sequential, andblock copolymers. A commercially available example of such a copolymer,which when quenched forms a mesocopolymer according to the presentinvention, is sold under the trademark "PETROTHANE" resin No. PP7300-KF(Quantum Chemical, Inc.).

The second class of copolymers according to the present invention, whichwhen quenched can provide the mesocopolymers of the above describedclass one copolymers, with another moiety grafted to the copolymerchain. For example, the other moiety can comprise a functional group,such as maleic anhydride or acrylic acid, grafted to the copolymerchain, to provide enhanced melt flow rates, as well as other properties.See, e.g., U.S. Pat. No. 4,003,874, and British Patent No. 1,393,693,the disclosures of which are herein incorporated by reference. Acommercially available example of such a copolymer is sold under thetrademark "PLEXAR" 420 (Quantum Chemical, Inc.).

The third, and final, general class of copolymers according to thepresent invention, which when quenched can provide the mesocopolymers,comprise a polypropylene homopolymer with a moiety, such as maleicanhydride or acrylic acid, grafted to the polymer chain. A commerciallyavailable example of such a copolymer is sold under the trademark"ADMER" QF551A (Mitsui Plastics, Inc.).

In a preferred embodiment, the mesocopolymer comprises a class onecopolymer of propylene monomer with a discernable amount of at least oneother monomer. Preferably, the propylene monomer will comprise fromabout 1% to about 99%, more preferably from about 50% to about 99%, andmost preferably from about 91% to about 99% by weight of themesocopolymer, with the remainder of the mesocopolymer comprising theother monomer, or monomers. The monomers to be combined with propyleneto form the mesocopolymers according to the present invention caninclude any monomer that would polymerize with propylene in the presenceof a suitable catalyst, including ethylene, butylene, pentene,methylpentene, and the like. Preferred monomers include ethylene andbutylene, with ethylene being particularly preferred.

In a particularly preferred embodiment, the mesocopolymer according tothe present invention comprises a copolymer of an ethylene monomer witha propylene monomer, that is quenched to provide the mesophase form ofthe copolymer. Preferably, the ethylene monomer comprises from about 1%to about 25%, more preferably from about 1% to about 20%, and mostpreferably from about 1% to about 10% by weight of the mesocopolymer,with the remaining monomer comprising propylene.

The mesocopolymer of the present invention can also be formed when thecopolymer is blended in polypropylene homopolymer at from about onepercent to about ninety nine percent by weight. A commercially availableexample of such a mixture is Shell resin FC05N, an ethylene-propylenecopolymer mixed at a level of 14 percent by weight to 86 percent byweight of a polypropylene homopolymer. As with the copolymer alone, theblend of copolymer and homopolymer must be quenched immediately afterextrusion to provide a mesocopolymer according to the present invention.

Optional Adhesive Layers

As noted above, the multilayered barrier structure 30 according to thepresent invention may also include optional adhesive layers 40, asillustrated in FIG. 2, interposed between the moisture barrier layer(s)34 and the gas barrier layer 32. The adhesive layers 40 serve to adherethe gas barrier layer 32 and moisture barrier layers 34 together, whenthe selected materials comprising those layers are not naturallycompatible, and therefore, not able to adhere to one another aftercoextrusion. For example, when the gas barrier layer 32 is comprised ofEVOH copolymer, and the moisture barrier layers 34 are comprised of amesopolymer blend of mesomorphous polypropylene and polybutylene,adhesive layers 40 are required to adhere the layers into a unitary,multilayered barrier structure 30 according to the present invention.

When an adhesive layer 40 is employed, the adhesive layer 40 should becomprised of materials which provide structural integrity to themultilayered barrier structure 30 of the present invention, withoutsubstantially affecting the barrier properties of the gas barrier layer32 and moisture barrier layers 34. In this regard, it will be preferredto use a mesocopolymer in the adhesive layer 40, since adhesivemesocopolymers exhibit the same advantageous properties as themesomorphous polypropylene, mesopolymer blends, and/or mesocopolymerscomprising the moisture barrier layer 34 of the multilayered barrierstructure 30 of the present invention.

It will be appreciated that adhesion between the gas barrier layer 12and moisture barrier layer(s) 14 can always be achieved by utilizing ablend of polymer in either, or both, of these layers, wherein at leastone of the polymers employed is a constituent polymer of both the gasbarrier 12 and moisture barrier 14 layers. For example, in a structuresuch as illustrated in FIG. 1, by using mesomorphous polypropylene (mPP)in the moisture barrier layer(s) 14 and a blend of EVOH and mPP in thegas barrier layer 12, the mPP appearing in both layers will result in anatural adhesion between the moisture barrier layer(s) 14 and gasbarrier layer 12, such that the need for an additional adhesive layer(s)40 will be eliminated. However, it will also be appreciated thatutilization of blends of polymers in the gas barrier layer 12 may resultin a reduction in the barrier properties of the multilayered barrierstructure 10.

Nonlimiting examples of adhesive layers 40 according to the presentinvention include functionalized polyolefins, such as anhydride modifiedpolypropylenes, acid modified polyolefins, acid/anhydride modifiedpolyolefins, or other similar adhesive polymers, copolymers or blends,such as ethylene vinyl acetate copolymer (EVA). Examples of preferredadhesive polymers include that sold under the trademark "ADMER" QF551A,a polypropylene graft copolymer adhesive (Mitsui Plastics, Inc.), andthat sold under the trademark "PLEXAR" 420, a propylene/ethylenecopolymer adhesive (Quantum Chemical Corp.).

It will be appreciated that the adhesive layers 40 can comprisefunctionalized derivatives of mesocopolymers that exhibit many or all ofthe advantageous properties, such as radiation resistance, and increasedtoughness, heat-sealability, softness and/or quietness, as well asproviding sufficient adhesion to affix the moisture barrier layer 34 andgas barrier layer 32 together. For example, it is within the scope ofthe present invention for functionalized adhesive copolymers, such asthose sold under the trademarks "ADMER" and "PLEXAR" to comprise themoisture barrier layer 14 of the present invention, quenched to preservethe mesophase form of the mesocopolymer after hot melt extrusion. Insuch an embodiment, the adhesive moisture barrier layer 14 could beaffixed to other layers or surfaces to provide for specializedmultilayered barrier structures 10 according to the present invention10. For example, an adhesive moisture barrier layer 14 could have awoven or nonwoven layer affixed thereto, to provide a more comfortablesurface against a wearers skin when the multilayered barrier structure10 is incorporated into an ostomy pouch or the like. However, it willalso be appreciated that any adhesive which is compatible with the gasbarrier layers 12 and moisture barrier layers 14 according to thepresent invention, is considered to fall within the scope of the presentinvention.

Tempering Additives

As noted above, utilization of mesophase propylene-based materials, suchas mesomorphous polypropylene, mesopolymer blends, and/ormesocopolymers, in the moisture barrier layer 14 of the multilayeredbarrier structure 10 can result in a softer and/or quieter structurethan a comparable structure containing crystalline polypropylene. It hasalso been discovered that incorporation of a tempering additive, as thatterm is defined herein, into one or more of the layers of themultilayered barrier structure 10 results in a structure which isquieter when wrinkled or rustled, and/or which is softer in terms ofcompliability and drape, than the corresponding structure lacking in thetempering additive. Nonlimiting examples of tempering additives includeethylene copolymers, such as ethylene vinyl acetate copolymer (EVA) andethylene acrylic acid copolymer (EAA), polybutylene, polybutylenecopolymers, or combinations thereof. Preferred tempering additivesinclude EVA, EAA, polybutylene, and combinations thereof.

In a preferred embodiment, an effective amount of the tempering additiveis incorporated into the moisture barrier layer 14, either as the secondpolymer of the mesopolymer blend, or as an optional additive with themesomorphous polypropylene, mesopolymer blend, and/or mesocopolymer ofthe moisture barrier layer 14. For example, the moisture barrier layer14 of the present invention can comprise a mesopolymer blend with EVAcopolymer incorporated therein. Incorporation of EVA copolymer into themoisture barrier layer 14 of the multilayered barrier structure 10according to the present invention results in a multilayered barrierstructure 10 which is substantially quieter (as measured by frequency ofsound emitted in Hertz) when wrinkled or rustled, than a comparablestructure containing crystalline polypropylene and/or crystallinecopolymers. Furthermore, incorporation of EVA copolymer into themoisture barrier layer 14, or other layers of the multilayered barrierstructure 10, can lower the modulus (Young's Modulus) of the moisturebarrier layer 12, resulting in a softer multilayered barrier structure10.

Other Additives

Totally optionally, to provide specific additional properties to themultilayered barrier structure 10 of the present invention, the moisturebarrier layer(s) 14, the gas barrier layer 12, and/or the adhesivelayers 40, may also contain conventional additives such as antistaticmaterials, pigments, dyes, fillers, plasticizers, ultraviolet absorbers,quenching agents such as mineral oil, and the like. However, themesophase propylene-based materials, including the mesomorphouspolypropylene, mesopolymer blends, and/or mesocopolymers, of themoisture barrier layer 14 do not require any stabilizers, anti-oxidantsor the like to enable the mesophase propylene-based materials, andaccordingly, the resulting moisture barrier layer 14 and multilayeredbarrier structure 10, to withstand the effects of ionizing radiation,and still substantially maintain the structural integrity of themultilayered barrier structure 10 for a useful period of time afterirradiation.

Properties of Multilayered Barrier Structures

In general, non-chlorine containing organic polymers, such as thepreferred EVOH copolymer comprising the gas barrier layer 12 of themultilayered barrier structure 10 of the present invention, rapidlydegrade after being exposed to ionizing radiation, such as gamma orelectron-beam radiation. Furthermore, the penetrating nature of ionizingradiation would be expected to cause such a degradation of non-chlorinecontaining organic polymers, even when layered within a multilayeredstructure or film. Surprisingly, incorporation of a gas barrier layer 32and optional adhesive layers 40, in conjunction with one or moremoisture barrier layers 34, into a multilayered barrier structure 30according to the present invention, results in a multilayered barrierstructure 30 with increased resistance to ionizing radiation.Specifically, even after ionizing radiation dosages from about 1 kGy(0.1 Mrad) to 100 kGy (10.0 Mrad), the multilayered barrier structure 30degrades at a substantially slower rate than a comparable structure withmoisture barrier layers lacking mesomorphous polypropylene, mesopolymerblends, and/or mesocopolymers.

In addition to increased radiation resistance, the combination of amoisture barrier layer 14 and a gas barrier layer 12 into a multilayeredbarrier structure 10 according to the present invention synergisticallyincreases the softness (i.e, decreases the stiffness, as measured by theYoung's Modulus and the yield stress), the toughness (as measured by thefracture strain), and the quietness (as measured in Hertz (Hz) of soundemitted), of the multilayered barrier structure 10 above that whichwould be expected under the Rule of Mixtures, as that term is definedabove. In addition, this synergistic effect on the softness, toughness,and/or quietness of the multilayered barrier structure 10 can be furtherenhanced when a tempering additive, as that term is defined above, isincorporated into the moisture barrier layer 14 of the multilayeredbarrier structure 10. Also, when using a moisture barrier layer 14formed from mesopolymer blends according to the present invention, themultilayered barrier structures 10 can exhibit enhanced properties whichare, at least in part, characteristic of the second polymers used in themesopolymer blends of the moisture barrier layers 14. For example, useof polybutylene along with mesomorphous polypropylene in a mesopolymerblend comprising the moisture barrier layers 14 enhances the heatsealability and toughness of the overall multilayered barrier structure10.

Furthermore, the radiation resistance provided by mesophasepropylene-based materials, such as mesomorphous polypropylene,mesopolymer blends, and/or mesocopolymers, serves to maintain theseenhanced characteristics for a useful period of time after ionizingirradiation at sterilization dosages. Thus, the multilayered barrierstructure 10 of the present invention can withstand ionizing radiation,such as gamma radiation, which is employed to sterilize the structure oran article formed therefrom. Generally, it is desirable that the dosageof gamma radiation be in the range from about 1 kGy (0.1 Mrad) to about100 kGy (10 Mrad), and preferably in the range from about 10 kGy (1Mrad) to about 60 kGy (6 Mrad) for sterilization of medical articles.

Importantly, the elimination of chlorine-containing compounds ascomponents of the gas barrier layer 12, moisture barrier layers 14,optional adhesive layers 40, or as additives to these layers, providesan environmentally compatible, multilayered barrier structure 10, whichcan be disposed of, such as through incineration, without endangeringhumans. Thus, various environmental hazards associated with the disposalof typical barrier materials, such as poly(vinylidene chloride) (PVDC)and poly(vinyl chloride) (PVC), can be avoided. In particular, materialssuch as PVDC and PVC release hazardous substances, such as hydrochloricacid (HCl), polychlorinated dibenzodioxin, and furan toxins duringincineration. In contrast, the materials comprising the multilayeredbarrier structure 10, according to the present invention are broken downto environmentally compatible water and carbon dioxide duringincineration.

Methods of Preparation

The process of blending known mixtures of polymers is well known tothose skilled in the art. See e.g., Mathews, Polymer Mixing Technology,Chapter 3 (Applied Science Publishers, Essex, England, 1982), thedisclosure of which is herein incorporated by reference. In the case ofthe present invention, the method of blending involves the use of anextruder by feeding the polymers (in the proper weight percentages, andwhere need be, after being dry-blended or compounded together) through aheated coextrusion process. Thus when a mesopolymer blend is to beemployed, polypropylene and the second polymer are first dry blendedtogether prior to being melt extruded as the moisture barrier layer 14.Furthermore, the non-chlorine containing organic polymer of the gasbarrier layer 12, and functionalized polyolefin of the optional adhesivelayer 40, are heated and coextruded with the moisture barrier layer 14to form the multilayered barrier structure 10 according to the presentinvention.

Coextrusion is a polymer processing method for bringing diversepolymeric materials together to form unitary layered structures, such asfilms, sheets, fibers, and tubing. This allows for unique combinationsof materials, and for structures with multiple functions, such as,barrier characteristics, radiation resistance, and heat sealability. Bycombining coextrusion with blown film processing, film structures can bemade which have no inherent waste and much lower capital investment overflat film coextrusion. However, flat film processing techniques providean excellent method for making the multilayered barrier structures 10,30according to the present invention.

Component polymer or copolymer materials according to the presentinvention can be coextruded from the melt state in any shape which canbe rapidly cooled to obtain a multilayered barrier structure 10 with amoisture barrier layer 14 which includes mesophase propylene-basedmaterials. The shape and/or thickness of the coextruded structure willbe dependent upon the efficiency of the particular extrusion equipmentemployed and the quenching systems utilized. Generally, films and tubesare the preferred coextruded structures. Only under appropriate, lowtemperature conditions (i.e., below 60° C.) can multilayered barrierstructures 10 be uniaxially, biaxially or multiaxially oriented tofurther enhance their barrier and physical properties without losing themesophase form of polypropylene or mesocopolymers in the moisturebarrier layer(s) 14.

To obtain multilayered barrier structures 10 with a moisture barrierlayer 14 having mesophase propylene-based materials, such asmesomorphous polypropylene, mesopolymer blends, and/or mesocopolymers,the coextruded structures must be quenched in a manner such that themesophase form of polypropylene and/or mesocopolymer is obtained.Miller, "On the Existence of Near-Range Order in IsotacticPolypropylenes", in Polymer, One, 135 (1960), and U.S. Pat. No.4,931,230, both of the disclosures of which are herein incorporated byreference, disclose suitable methods known to those skilled in the artfor the preparation of mesophase form of polypropylene.

As described by these publications, various known methods of quenchingas soon as possible, and preferably, immediately after extrusion, can beused to obtain a mesomorphous polypropylene homopolymer, mesopolymerblend, and/or mesocopolymer having the mesophase form of polypropyleneand/or mesocopolymer therein. Quenching methods include plunging thecoextruded structure into a cold liquid, for example, an ice water bath(i.e., quench bath), spraying the coextruded structure with a liquid,such as water, hitting the film with a stream of cold air, and/orrunning the coextruded structure over a cooled roll, quench roll, ordrum.

The coextruded multilayered barrier structure 10 of the presentinvention is preferably quenched immediately after extrusion by contactwith a quench roll, or by being plunged into a quench bath. For a filmthickness of from about 6μ to about 625μ, where a quench roll is used,roll temperature is maintained at a temperature below about 38° C.,preferably below about 24° C., and the coextrudate is generally incontact with the quench roll until solidified. The quench roll should bepositioned relatively close to the coextruder die, the distance beingdependent on the roll temperature, the extrusion rate, the filmthickness, and the roll speed. Generally, the distance from the die tothe quench roll is about 0.25 cm to 5 cm. Where a quench bath is used,the bath temperature is preferably maintained at a temperature belowabout 4° C. The bath should be positioned relatively close to the die,generally from about 0.25 cm to 13 cm from the die to the quench bath.

As noted above, the coextruded multilayered barrier structure 10according to the present invention should not be subjected to anytreatment, such as orientation or stretching, at temperatures above 60°C. Specifically, the employment of such treatment techniques attemperatures above 60° C. would transform the mesophase form ofpropylene-based materials in the moisture barrier layer 14 of themultilayered structure 10 to predominantly undesired crystalline form ofpropylene-based materials.

Usefulness of the Invention

In a preferred construction, the multilayered barrier structure 10according to the present invention comprises a five-layer barrier film30 such as illustrated in FIG. 2, with a core gas barrier layer 32 ofEVOH copolymer, two intermediate adhesive layers 40 of a functionalizedpolyolefin, and two outer moisture barrier layers 34 comprised of amesophase propylene-based materials, such as mesomorphous polypropylenehomopolymer, a mesopolymer blend of mesomorphous polypropylene andpolybutylene, EVA copolymer, EAA copolymer, a mesocopolymer, orcombinations of any of these polymers or copolymers.

Multilayered barrier films 10 according to the present invention will beespecially useful in ostomy pouch applications, where security fromodor, integrity of the device, and integrity of the underlying materialsare requirements. Multilayered barrier films 10 can be die cut and heatsealed with conventional equipment, and are compatible with currentattachment systems and ostomy pouch manufacturing practices. Since themultilayered barrier films 10 are moisture resistant both inside andout, the resulting ostomy pouch is capable of being worn during swimmingand showering. Optionally, with incorporation of a polymeric temperingadditive, such as EVA copolymer, EAA copolymer, polybutylene,polybutylene copolymers, or combinations thereof, into various layers ofthe barrier film 10, the resulting ostomy pouch can be quieter whenwrinkled or rustled during the movements of a wearer of such a pouch. Inaddition, other useful articles such as tapes, tubings, containers,transdermal drug-delivery patches and various packaging materials canalso be formed from the multilayered barrier film 10 of the presentinvention. Thus, the multilayered barrier film 10 of the presentinvention is useful to form or cover a protective environment from anexternal environment, such that moisture and/or gases cannotsubstantially pass through to a degradable product contained therein, ora surface covered thereby. For example, the multilayered barrier film 10can be used to contain a food product or a pharmaceutical product in aprotected environment, to which moisture and/or gases from the externalenvironment cannot substantially pass into. Similarly, the multilayeredbarrier film 10 can comprise a transdermal drug delivery patch, ormedical tape, or an ostomy pouch, which protects the body of a mammal,or the waste products generated by the mammal, from degradation due toexposure to moisture and/or gases in the external environment.

Other Layers

Articles formed from the multilayered barrier structures 10,30 need notbe limited to three-layered and five-layered examples illustrated inFIGS. 1 and 2. In addition, these multilayered barrier structures 10,30can be further modified for specialty applications by adding additionallayers thereto. For example, a specialty ostomy pouch comprising amultilayered barrier structure 10 of the present invention could beformed by laminating a fabric backing of a woven or nonwoven material(not shown) to a surface of the ostomy pouch. This fabric backing wouldact to provide a soft layer against a wearer's skin, and thus make theostomy pouch more comfortable and non-clinging.

A fabric backing could be applied to the multilayered barrier structure10 of the present invention in a number of different ways. For example,a layer of a nonwoven material, formed from a polymer such aspolypropylene, could be affixed to the multilayered barrier structure 10of the present invention by an intervening adhesive layer. Preferably,such an adhesive layer would comprise a functionalized mesocopolymeraccording to the present invention. In addition, a fabric backing couldbe affixed to the multilayered barrier structure 10 by running bothlayers through hot rollers or nips, that would heat seal the fabric andbarrier layers together. In such a heat sealing operation, it would bepreferred to maintain the hot rollers at sufficient temperature toprovide an effective heat seal between the layers without substantiallyaffecting the mesophase form of the mesomorphous polypropylene,mesopolymer blends, and/or mesocopolymers of the moisture barrierlayer(s) 14 of the multilayered barrier structure 10.

As an alternative, a fabric backing could be applied to the multilayeredbarrier structure 10 of the present invention by affixing a web of meltblown microfibers thereto. For example, melt blown polymer microfiberscould be hot melt extruded from a die into a high velocity air stream,and onto a surface of the multilayered barrier structure 10 according tothe present invention. See, e.g., Report No. 4364 of the Naval ResearchLaboratories, published May 25, 1954, entitled "Manufacture of SuperfineOrganic Fibers", by V. A. Wente et al , and V. W. Wente et al.,"Superfine Thermoplasitic Fibers", 48, Industrial Engineering Chemistry,1342 (1956), both of the disclosures of which are herein incorporated byreference. In a preferred embodiment, the melt blown microfiber webaffixed to at least one side of the multilayered barrier structure 10could be formed of mesomorphous polypropylene, mesopolymer blends,and/or mesocopolymers, by quenching the hot blown microfibersimmediately after extrusion. For example, the microfibers could bequenched by spraying the fibers with a liquid such as water, or bycollecting the fibers on the multilayered barrier structure 10 that isin contact with a cooled collector drum or roll.

The following non-limiting examples are provided to further illustratethe invention.

EXAMPLES 1-4 AND 6, AND COMPARISON EXAMPLES 5 AND 7-10

Ten, five-layered coextruded barrier films were made using a flat filmprocess consisting of 3 extruders, a 5-layer feedblock sold under thetrademark "CLOEREN" (Cloeren Company, Orange, Tex.), and a singlemanifold film extrusion die. The barrier films were generally coextrudedat a film thickness of about 75μ, with each moisture barrier layer(hereinafter layer "A") being about 30μ thick, each adhesive layer(hereinafter layer "B") being about 4μ thick, and the gas barrier layer(hereinafter layer "C") being about 8μ thick. The construction of thefive-layered barrier films corresponded to the multilayered structureillustrated in FIG. 2 herein.

Layer A comprised mixtures by weight of polypropylene resin (hereinafter"PP") (PP3576; Fina Oil and Chemical Co.; melt index=9 g/10 min.), andpolybutylene resin (hereinafter "PB") (PB400; Shell Chemical Co.; meltindex=20 g/10 min.). Layer B comprised a polypropylene based adhesivelayer of a resin sold under the trademark "ADMER" (Mitsui Plastics,Inc.; melt index=5.7 g/10 min.). Layer C was made of an ethylene-vinylalcohol copolymer (hereinafter "EVOH") (sold under the trademark "EVAL",E105 Evalca Co; melt index=5.5 g/10 min.).

The PP/PB mixtures were dry blended before being melted and coextruded.Film extrusion conditions for Examples 1-4 and 6, and ComparisonExamples 5 and 7-10 are given in Table 1. Table 2 lists specific filmconstructions for layer A of the Example and Comparison Example filmsand their casting roll (quench) temperatures. The temperature of thequench roll for Examples 1-4 was maintained at 10° C., and at -1° C. forExample 6, in order to control the mesomorphous structure of thepolypropylene in the polymer blend. The multilayered films werecoextruded onto a quench roll spaced 2.54 cm from the extrusion die. Thefilms were in contact with the quench roll for about 2 seconds and werecoextruded at a rate of about 17 meters per minutes (mpm). The adhesivelayer and barrier layer constructions were kept constant across all ofthe Examples and Comparison Examples.

Thickness of each layer in the multilayered barrier films of Examples1-4 and 6, and Comparison Examples 5 and 7-10 was determined via opticalmicroscopy from film cross-sections. Samples of each of the Examplefilms were cut and trimmed, and then embedded in 3M an electrical resinsold under the trademark "SCOTCHCAST" electrical resin No. 8 (3M, St.Paul, Minn.). The films were then cut into cross-sections using amicrotome. Specimens were placed on a glass slide in immersion oil witha cover slip placed on top. Layer thicknesses were then determined viatransmitted bright field optical microscopy. Values for the moisturebarrier layer thicknesses (designated as layers 1A and 2A), adhesivelayer thicknesses (designated as layers 1B and 2B), core gas barrierlayer thickness (designated as layer C), and total film thickness areshown in Table 3.

                  TABLE 1    ______________________________________    Film extrusion conditions for Examples 1-4 and 6,    and for Comparison Examples 5 and 7-10.            Melt           Screw   Die            Temperature    Speed   Temperature    Layer   (°C.)   (RPM)   (°C.)    ______________________________________    A       221            59      232    B       232            18      232    C       237            20      232    ______________________________________

                  TABLE 2    ______________________________________    Weight percentage ratio of polypropylene (PP) to    polybutylene (PB), and casting (quench) roll    temperatures for layer A of Examples 1-4 and 6, and    Comparison Examples 5 and 7-10.                   Ratio    Casting Roll    Example        PP:PB    Temperature    Number         (wt %)   (°C.)    ______________________________________    Ex. 1          100/0    10    Ex. 2          80/20    10    Ex. 3          50/50    10    Ex. 4          20/80    10    Comp. Ex. 5     0/100   10    Ex. 6          50/50    -1    Comp. Ex. 7    100/0    66    Comp. Ex. 8    80/20    66    Comp. Ex. 9    50/50    66    Comp. Ex. 10   50/50    66    ______________________________________

                  TABLE 3    ______________________________________    Moisture barrier layer thicknesses (1A and 2A),    adhesive layer thicknesses (1B and 2B), gas barrier    layer thickness (C), and total film thickness in    microns (μ) for Examples 1-4 and 6, and for    Comparison Examples 5 and 7-10.           Layer   Layer   Layer Layer Layer Film           1A      1B      C     2B    2A    Thickness    Example           (μ)  (μ)  (μ)                                 (μ)                                       (μ)                                             Total    ______________________________________    Ex. 1  37      5       11    2     40    95    Ex. 2  38      4       12    5     39    97    Ex. 3  37      3       8     4     35    87    Ex. 4  32      3       11    3     39    86    Comp.  37      2       14    5     40    98    Ex. 5    Ex. 6  35      2       10    3     35    85    Comp.  38      5       12    3     37    94    Ex. 7    Comp.  31      5       11    5     30    81    Ex. 8    Comp.  26      4       12    7     31    80    Ex. 9    Comp.  27      5       12    5     34    82    Ex. 10    ______________________________________

The crystalline structure, or mesomorphous structure, for each of themultilayered barrier films of Examples 1-4 and 6, and for ComparisonExamples 5 and 7-10 was determined by wide-angle x-ray diffraction(WAXD). Graphical illustrations of the WAXD scans for each of theExample and Comparison Example films are shown in FIGS. 3 through 12herein. The mesophase form (i.e., mesomorphous polypropylene) is clearlyshown in FIGS. 3-6 and 8. FIG. 7 shows the sharp peaks associated withcrystalline polybutylene, while the very sharp peaks in the WAXD scanshown in FIGS. 10-12 are due to the crystalline phases of bothpolypropylene and polybutylene. The WAXD data for polypropylene presentin the Example and Comparison Example films is summarized in Table 4.

                  TABLE 4    ______________________________________    Structure of the polypropylene homopolymer    and polymer blends of Examples 1-4 and 6, and for    Comparison Examples 5 and 7-10, as determined by WAXD.              Ratio                  Casting Roll    Example   PP/PB                  Temperature    Number    (wt %)    WAXD PP      (°C.)    ______________________________________    Ex. 1     100/0     Mesomorphous 10    Ex. 2     80/20     Mesomorphous 10    Ex. 3     50/50     Mesomorphous 10    Ex. 4     20/80     Mesomorphous 10    Comp. Ex. 5               0/100    na           10    Ex. 6     50/50     Mesomorphous -1    Comp. Ex. 7              100/0     Crystalline  66    Comp. Ex. 8              80/20     Crystalline  66    Comp. Ex. 9              50/50     Crystalline  66    Comp. Ex. 10              50/50     Crystalline  66    ______________________________________

The tensile properties for the barrier films of Examples 1-4 and 6 andComparison Examples 5 and 7-10 were determined on an INSTRON Model 1122machine using 5 cm××2.5 cm samples of the Example and Comparison Examplemultilayered barrier films. Each sample was deformed at a strain rate ofone thousand percent (1000%) per minute (sample gauge length of 5 cmsand a crosshead speed of 51 cms per minute) using ASTM D882-88procedures. In each case, at least three samples of each of the Exampleand Comparison Example films were measured for each value reported.Modulus values were calculated by taking modulus values determined usingthe INSTRON Model 1122 with the load cell amplifier switch set in the"IN" position and multiplying by two. When set in the "IN" position, adampening of the recorder pen servo occurs which (as demonstrated insubsequent analysis) can be corrected by multiplying by two. Effect ofmesomorphous polypropylene (mPP) composition on modulus (Young'sModulus, as measured in Mega Pascals (MPa)) is shown in FIG. 13 (lineA). As mPP concentration is reduced (or PB concentration in themesopolymer blend is increased) the multilayered barrier film becomesless stiff (i.e., softer). As can be seen in FIG. 13, the modulus valuesfor the mesopolymer blends are lower than would be expected from theRule of Mixtures, as defined herein, and illustrated at line B. Thissynergy in softness is further reflected in the yield stress results asshown in FIG. 14. As with FIG. 13, the actual yield stress valuesillustrated by line A are considerably less than those which would bepredicted under the Rule of Mixtures illustrated at line B. Furthermore,quenched (casting roll temperature of 10° C. or less) multilayeredbarrier films containing mPP in the outer layer blend were found to be24 to 30% less stiff than similar compositions with crystalline PP(casting roll temperature at 66° C.), as shown in Table 5.

                  TABLE 5    ______________________________________    Young's Modulus in Mega Pascals (MPa) of the multilayered    barrier films of Examples 1-4 and 6, and    Comparison Examples 5 and 7-10.               Ratio               Casting    Example    PP/PB      Modulus  Roll    Number     (wt %)     (MPa)    Temperature    ______________________________________    Ex. 1      100/0      752      10    Ex. 2      80/20      546      10    Ex. 3      50/50      462      10    Ex. 4      20/80      406      10    Comp. Ex. 5                0/100     386      10    Ex. 6      50/50      452      -1    Comp. Ex. 7               100/0      984      66    Comp. Ex. 8               80/20      780      66    Comp. Ex. 9               50/50      622      66    Comp. Ex. 10               50/50      600      66    ______________________________________

Resistance to permeation of oxygen and moisture vapor was measured forthe multilayered barrier films of Examples 1-4 and 6. Oxygentransmission rate (O₂ TR) was determined using an OX-TRAN 1000H machine(Mocon, Inc., Minneapolis, Minn.). O₂ TR was collected at 25° C. andzero percent (0%) relative humidity. A square sample of each multilayerfilm was placed in the testing cell of the OX-TRAN oxygen permeabilitytester. Two samples of each film were tested in adjacent cells. Sincethe OX-TRAN 1000H machine has ten test cells, up to five films could beexamined at any one time.

Each cell was purged for at least 24 hours with a "carrier" gas ofnitrogen containing 1-3% hydrogen prior to testing, to remove anyresidual oxygen in the sample, cell and system. After purging wascompleted, a sample of the gases in each cell was tested for residualoxygen content or oxygen "leak rate". The leak rate value determined ateach cell was used as the cell's residual oxygen baseline.

Next, each cell was conditioned for another 24 hours by passing 100%oxygen over one side of the sample. Oxygen on the other side of thesample was measured after this conditioning period. This total oxygencontent included the amount of oxygen which permeated through the filmplus any residual oxygen in the system. To obtain oxygen transmissionrate through the film, the leak rate value was subtracted from the totaloxygen measured.

Oxygen transmission rate data was collected for each film at 25° C. and0% relative humidity. The values reported are the average of ratesdetermined for two samples. Since oxygen transmission rate is inverselyproportional to thickness, all values were normalized to a standard gasbarrier layer thickness of 25μ by multiplying the oxygen transmissionrate value by the ratio of barrier layer thickness (as reported in Table3 herein) to 25μ.

Moisture vapor transmission rate (MVTR) for the Example films wasdetermined using a PERMATRAN-W6 (Mocon, Inc., Minneapolis, Minn.). MVTRdata was collected at 38.6° C. and one-hundred percent (100%) relativehumidity. The reported values are the average of the values obtained forat least three samples of each Example film. Since MVTR is inverselyproportional to thickness, all values were normalized to a standardmoisture barrier layer thickness of 25μ (microns) by multiplying theMVTR value by the ratio of moisture barrier layer thickness (being thesum of the moisture barrier and adhesive layer thicknesses, as reportedin Table 3 herein) to 25μ. The oxygen transmission rates (O₂ TR) andmoisture vapor transmission rates (MVTR) for Examples 1-4 and 6 arereported in Table 6. These rates demonstrate good oxygen and moisturebarrier properties for the Example films of the present invention.

                  TABLE 6    ______________________________________    Oxygen transmission rates (O.sub.2 TR), as expressed in    cc/m.sup.2 /day-atmosphere, and moisture vapor    transmission rates (MVTR), as expressed in g/m.sup.2 /day-    atmosphere, for Examples 1-4 and 6.                   Casting          Ratio    Roll    Ex.   PP/PB    Temp.    O.sub.2 TR MVTR    No.   (Wt %)   (°C.)                            (cc/m.sup.2 /d-atm)                                       (g/m.sup.2 /d-atm)    ______________________________________    1     100/0    10       2.0        13.8    2     80/20    10       2.2        14.5    3     50/50    10       1.5        16.4    4     20/80    10       2.1        14.9    6     50/50    -1       2.0        18.3    ______________________________________

COMPARISON EXAMPLES 11-16

Six, five-layered coextruded barrier films were made on a standardpolyethylene type, blown-film processing line using a five-layer blownfilm die. The barrier films were coextruded at a thickness of 75μ. Theconstruction of the five-layered barrier films was analogous to themultilayered barrier structure construction illustrated in FIG. 2herein. In particular, each moisture barrier layer (hereinafter "layerA") comprised a 50/50 mixture by weight of polypropylene (PP) (pp 3150;melt index=0.8 g/10 min.; Fina Oil and Chemical Co.) and polybutylene(PB)(PB 200; melt index 1.8 g/10 min. for Comparison Examples 11-13; andPB 1710A; melt index 1.0 g/10 min. for Comparison Examples 14-16; ShellChemical Co.). Each adhesive layer (hereinafter "layer B") comprised apolypropylene copolymer (sold under the trademark "PLEXAR" 420; meltindex=2.5 g/10 min.; Quantum Chemical Corp.). The gas barrier layer(hereinafter "layer C"), comprised an ethylene-vinyl alcohol polymer(EVOH) (sold under the trademark "EVAL" E151B; melt index=1.6 g/10 min.;Evalca Co.). The PP/PB mesopolymer blends were precompounded beforebeing melted and coextruded.

The six barrier film constructions of Comparison Examples 11-16 aregiven in Table 7. Each of the films was cross-sectioned, and individuallayer thicknesses were determined by optical microscopy according to thesame procedures as for Examples 1-4 and 6 and Comparison Examples 5 and7-10. Extrusion processing conditions for each of the layers of themultilayered barrier films of Comparison Examples 11-16 are shown inTable 8. The films were made 0.24 m wide at a 21 meters per min. (mpm)line speed. None of Comparison Examples 11-16 were quenched after hotmelt coextrusion. Thus, these samples did not include any discernableamount of mesomorphous polypropylene in the moisture barrier layers.

                  TABLE 7    ______________________________________    Individual layer thicknesses in microns (μ) for the    barrier film constructions of Comparison Examples 11-16.    Comparison             Layer C   Layer BX2 Layer AX2                                         Layer AX2    Example  Thickness Thickness Thickness                                         Thickness    Number   (Microns) (Microns) (Microns)                                         (Microns    ______________________________________    11       4         4 × 2                                 33 × 2    12       8         4 × 2                                 31 × 2    13       15        4 × 2                                 27 × 2    14       4         4 × 2       33 × 2    15       8         4 × 2       31 × 2    16       15        4 × 2       27 × 2    ______________________________________

                  TABLE 8    ______________________________________    Individual processing conditions for each of the layers    of the multilayered barrier film constructions of    Comparison Examples 11-16.    Individual    Layer    Process  Comp.   Comp.   Comp. Comp. Comp. Comp.    Conditions             Ex. 11  Ex. 12  Ex. 13                                   Ex. 14                                         Ex. 15                                               Ex. 16    ______________________________________    Layer C Extruder (4 cm)    Screw Speed             25      50      100   25    50    100    (rmp)    Melt     219     219     220   222   220   223    Temperature    (°C.)    Amps     12      15      19    11    15    19    Layer B Extruder (4 cm)    Screw Speed             75      75      75    75    75    75    (rmp)    Melt     217     217     217   219   219   219    Temperature    (°C.)    Amps     14      14      14    14    14    14    Layer A Extruder (6 cm)    Screw Speed             97      97      97    97    97    97    (rmp)    Melt     238     238     238   256   254   257    Temperature    (°C.)    Amps     102     102     102   108   108   108    Die      216     216     216   216   216   216    Temperature    (°C.)    Blow Up  2:1     2:1     2:1   2:1   2:1   2:1    Ratio    Frost    61      61      61    61    61    61    Line (cm)    ______________________________________

The tensile properties of each of the six barrier films of ComparisonExamples 11-16 were performed on an INSTRON Model 1122 machine accordingto the same procedures as employed in Examples 1-4 and 6, and ComparisonExamples 5 and 7-10. Yield strain, fracture strain, yield stress,fracture stress and Young's modulus was obtained for each of ComparisonExamples 11-16, and are shown in Table 9. At least three samples of eachof the Comparison Example films were measured for each value reported.

                  TABLE 9    ______________________________________    Yield strain, fracture strain, yield stress, fracture    stress, and Young's modulus in Mega Pascal (MPa) for    each of Comparison Examples 11-16.          Layer C  Yield   Fracture                                  Yield Fracture                                               Mod-    Comp  Thick-   Strain  Strain Stress                                        Stress ulus    Ex.   ness (μ)                   (%)     (%)    (MPa) (MPa)  (MPa)    ______________________________________    11    4        21      364    23    25     584    12    8        22      370    26    25     638    13    15       20      370    35    32     806    14    4        25      380    24    25     564    15    8        26      325    25    24     608    16    15       20      372    32    27     810    ______________________________________

Comparison Examples 11-16 illustrate that multilayered barrier films canbe made on a blown film coextrusion line, and have properties similar tothose produced via flat film coextrusion processing. For example, themodulus values for non-quenched Comparison Examples 12 and 15 arecomparable to those of Comparison Examples 9 and 10. Furthermore, sincequenched multilayered barrier structures in accordance with the presentinvention can be made by flat film coextrusion, as shown in Examples 2-3and 6, it is reasonable to expect that with appropriate modification toinclude quenching of the extrudate, that the blown film coextrusionprocessing disclosed in Comparison Examples 11-16 could also be utilizedto form the multilayered barrier structures of the present invention.

EXAMPLES 17, 19, 21, 23, 25 and 27-31, and COMPARISON EXAMPLES 18, 20,22, 24 AND 26

Fifteen, five-layered, coextruded barrier films were made according tothe same procedures as for Examples 1-4 and 6, and Comparison Examples 5and 7-10 herein. Layer A was made from 50/50 mixtures by weight ofpolypropylene and polybutylene based resins. The polypropylenes usedwere Nos. PP3374 (melt index=2.5 g/10 min.) and PP3576 (melt index=9g/10 min.), (Fina Oil and Chemical Co.). The polybutylenes employed wereNos. PB 8310 (melt index=3 g/10 min.), DP1560 (melt index=4 g/10 min.),PB 300 (melt index=4 g/10 min.), PB 8340 (melt index=4 g/10 min.), andPB 400 (melt index=20 g/10 min.), (Shell Chemical Co.). Numbers PB 8310and PB 8340 are polybutylene-ethylene copolymers, and No. DP1560 is apolybutylene-based special formulation (Shell Chemical Co.). Layer B wasmade of PLEXAR 420 (melt index=2.5 g/ 10 min.) (Quantum Chemical Co.).Layer C was made of EVOH, (sold under the trademark "EVAL", E105A) (meltindex 5.5 g/10 min.) (Evalea Co.) (Note: Examples 17 and 18 were madeusing a precompounded mixture of Fina PP3150 (melt index=0.8 g/10 min.),and PB1710A, melt index=1.0 g/10 min.).

The barrier film rolls were extruded onto casting rolls at eithertemperatures of 10° C. for Examples 17, 19, 21, 23, 25 and 27-31, or 66°C. for Comparison Examples 18, 20, 22, 24, and 26. All films werecoextruded at the rate of 10 meters per minute (mpm). Accordingly, forthose Comparison Example films cooled at 66° C., the crystalline phaseof polypropylene was present, instead of the mesophase of polypropylenefound in the Examples quenched at 10° C. The film coextrusion conditionsemployed for each of Examples and Comparison Examples are given in Table10.

The tensile properties of the barrier films of the Examples andComparison Examples were obtained as in Examples 1-4 and 6, andComparison Examples 5 and 7-10. Yield strain, fracture strain, yieldstress, fracture stress and Young's modulus, expressed in (MPa), forExamples 17, 19, 21, 23, 25, and 27-31 and Comparison Examples 18, 20,22, 24 and 26 are shown in Table 11. At least three samples for each ofthe Example and Comparison Examples barrier film were measured for eachvalue reported.

                                      TABLE 10    __________________________________________________________________________    Film coextrusion conditions and compositions employed for each layer of    Examples 17, 19, 21, 23, 25 and 27-31, and for Comparison Examples 18,    20, 22, 24 and 26.    __________________________________________________________________________    Individual     Comp.   Comp.   Comp.   Comp.   Comp.    Layer Process               Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex. Ex.    Conditions 17  18  19  20  21  22  23  24  25  26    __________________________________________________________________________    Layer A    PP Type    3150                   3150                       3374                           3374                               3374                                   3374                                       3374                                           3374                                               3374                                                   3374    PB Type    1710A                   1710A                       8310                           8310                               1560                                   1560                                       300 330 8340                                                   8340    Melt Temp. (°C.)               223 222 221 222 221 221 221 222 222 222    Screw Speed (RPM)               26  26  26  26  26  26  26  26  26  26    Layer B    Plexar ™ Type               420 420 420 420 420 420 420 420 420 420    Melt Temp. (°C.)               204 204 204 204 204 204 204 204 204 204    Screw Speed (RPM)               13  13  14  14  14  14  15  15  15  15     Layer C    EVOH Type  E105A                   E105A                       E105A                           E105A                               E105A                                   E105A                                       E105A                                           E105A                                               E105A                                                   E105A    Melt Temp. (°C.)               231 231 231 232 232 232 231 231 231 231    Screw Speed (RPM)               15  15  15  15  15  15  15  14  14  14    Die Temp. (°C.)               224 224 224 224 232 232 232 232 232 232    Cast Roll Temp (°C.)               <10 66  <10 66  <10 66  <10 66  <10 66    Film Thickness               71  84  61  71  74  64  59  53  66  58    (microns)    __________________________________________________________________________                        Individual                        Layer Process                                   Ex. Ex. Ex. Ex. Ex.                        Conditions 27  28  29  30  31    __________________________________________________________________________                        Layer A                        PP Type    3576                                       3576                                           3576                                               3576                                                   3374                        PB Type    8310                                       300 8340                                               1560                                                   400                        Melt Temp. (°C.)                                   221 231 233 232 232                        Screw Speed (RPM)                                   26  26  26  26  26                        Layer B                        Plexar ™ Type                                   420 420 420 420 420                        Melt Temp. (°C.)                                   204 204 204 204 204                        Screw Speed (RPM)                                   15  15  15  15  15                        Layer C                        EVOH Type  E105A                                       E105A                                           E105A                                               E105A                                                   E105A                        Melt Temp. (°C.)                                   232 231 231 237 242                        Screw Speed (RPM)                                   14  14  14  14  14                        Die Temp. (°C.)                                   232 232 232 232 232                        Cast Roll Temp (°C.)                                   <10 <10 <10 <10 <10                        Film Thickness                                   69  64  69  64  48                        (microns)    __________________________________________________________________________

                  TABLE 11    ______________________________________    Yield strain, fracture strain, yield stress,    fracture stress and Young's modulus for    Examples 17, 19, 21, 23, 25 and 27--31 and    Comparison Examples 18, 20, 22, 24, and 26.            Yield   Fracture  Yield Fracture            Strain  Strain    Stress                                    Stress Modulus    Example (%)     (%)       (MPa) (MPa)  (MPa)    ______________________________________    Ex. 17  18      430       16    28     454    Comp.   8       447       21    32     572    Ex. 18    Ex. 19  20      426       14    23     380    Comp.   21      411       17    25     450    Ex. 20    Ex. 21  16      429       16    24     492    Comp.   18      406       23    28     620    Ex. 22    Ex. 23  17      418       15    25     446    Comp.   23      345       20    26     496    Ex. 24    Ex. 25  18      462       15    27     426    Comp.   22      387       23    32     572    Ex. 26    Ex. 27  17      473       14    25     416    Ex. 28  15      427       17    24     468    Ex. 29  17      420       16    24     454    Ex. 30  15      468       17    26     508    Ex. 31  14      470       15    25     444    ______________________________________

The Example and Comparison Example films illustrate that multilayeredbarrier films can be made with outer layers comprised of blends ofpolypropylene of varying melt index combined with various polybutyleneand polybutylene copolymers. The mechanical property data of Table 11shows that those quenched multilayered barrier films made in accordancewith the principles of the present invention (i.e., Example Nos. 17, 19,21, 23, 25, and 27-31) have modulus values 10-26% less than theircorresponding nonquenched films (i.e., Comparison Example Nos. 18, 20,22, 24, and 26), and accordingly, are softer (less stiff) than thenonquenched films.

EXAMPLES 32-41

Ten, five-layered, coextruded barrier films were made using a flat filmprocess consisting of three extruders as described in Examples 1-4 and6. Layer A was made from mixtures of polypropylene (No. PP3576, meltindex=9 g/10 min.; or No. PP3374, melt index=2.5 g/10 min.; Fina Oil andChemical Co.) and polybutylene (No. PB400, melt index=20 g/10 min.; orNo. PB8340, melt index=4 g/10 min., Shell Chemical Co.). Layer B was ofPLEXAR-420 (melt index=2.5 g/10 min.; Quantum Chemical Co.) or ADMERQF551A (melt index=5.7 g/10 min.; Mitsui Plastics, Inc.). Layer C was anEVOH copolymer (No. E105, melt index=5.5 g/10 min; or No. G115, meltindex=14 g/10 min., or No. ES-G110, melt index=16, g/10 min.; EvalcaCo.). The process conditions for each layer of Examples 32-41 are shownin Table 12. The films were all made at 12 meters per minute (mpm), andwere quenched on a 14° C. casting roll to a 75μ thickness. The specificcompositions of each film of Examples 32-41 are given in Table 13.

                  TABLE 12    ______________________________________    Process conditions for each layer of Example films 32-41                Melt Temperature                             Screw Speed    Layer       (°C.) (RPM)    ______________________________________    A           227          59    B           227          14    C           231          10    ______________________________________

                  TABLE 13    ______________________________________    Compositions of each film of Examples 32-41    (all Example films were quenched at a    temperature of 14° C.).           Layer A  Layer B        Layer B  Layer C    Example           PP       PB       PP:PB Adhesive EVOH    ______________________________________    32     3576      400     80/20 PLEXAR ™                                            E105                                   420    33     3576      400     80/20 PLEXAR ™                                            G115                                   420    34     3576      400     50/50 PLEXAR ™                                            G115                                   420    35     3576      400     50/50 PLEXAR ™                                            E105                                   420    36     3374      400     50/50 PLEXAR ™                                            E105                                   420    37     3374      400     50/50 PLEXAR ™                                            G115                                   420    38     3576     8349     20/80 PLEXAR ™                                            G115                                   420    39     3576     8340     20/80 PLEXAR ™                                            3105                                   420    40     3374     8340     50/50 ADMER ™                                            E105                                   QF551A    41     3374     8340     50/50 ADMER ™                                            ES-G110                                   QF551A    ______________________________________

The tensile properties of each of the Example barrier films wereobtained as in Example and Comparison Example Numbers 11-31. Yieldstrain, fracture strain, yield stress, fracture stress and Young'smodulus are shown for Examples 32-41 in Table 14. At least three samplesfor each of the Example barrier films were measured for each valuereported.

                  TABLE 14    ______________________________________    Yield strain, fracture strain, yield stress, fracture    stress and modulus for Examples 32-41.           Yield    Fracture Yield  Fracture           Strain   Strain   Stress Stress Modulus    Example           (%)      (%)      (MPa)  (MPa)  (MPa)    ______________________________________    32     16       634      18     34     532    33     16       831      17     37     476    34     17       755      14     33     360    35     17       618      13     30     384    36     19       665      15     39     412    37     20       703      14     37     354    38     20       605      12     37     268    39     20       455      12     31     282    40     20       704      14     41     352    41     19       631      14     14     354    ______________________________________

Examples 32-41 illustrate that multilayered barrier films can be madewith outer layers comprised of blends of varying ratio, of polypropylenewith differing melt index in combination with polybutylene andpolybutylene copolymers, and with a core layer of EVOH copolymers whichhave varying mole percents of ethylene in the copolymers (44% for E105,48% for G115, and 53% for ES-G110). Examples 32-35 also show thatmodulus, and accordingly the softness of the barrier films, can beeffectively controlled by changing the mesomorphous polypropylene (mPP)ratio in the blend. Specifically, as the percent mPP is decreased from80% in Examples 32-33 to 50% in Examples 34-35, a corresponding drop inthe modulus of 25-28% is observed.

EXAMPLES 42-43

Two, three-layered, coextruded barrier films analogous to the filmconstructions illustrated in FIG. 1 were made using a flat film processby blending polypropylene (No. PP3374, melt index 2.5 g/10 min.; FinaOil and Chemical Co.) and polybutylene (No. PB8340; melt index 4.0 g/10min.; Shell Chemical Co.) as layer A, blending EVOH (No. E105; meltindex 5.5 g/10 min.; Evalca Co.) and ethylene vinyl acetate copolymer(EVA) (Elvax 660; Dupont, Inc.) for layer C, and eliminating adhesivelayer B. The films were made at 12 meters per minute, and were quenchedon a 14° C. casting roll to a 75μ thickness. The process conditions foreach layer of Examples 42 and 43 are shown in Table 15. The specificcompositions of each of the Example films are given in Table 16.

                  TABLE 15    ______________________________________    Process conditions for each layer of    Examples 42 and 43.                  Melt       Screw                  Temperature                             Speed    Layer         (°C.)                             (RPM)    ______________________________________    A             227        59    C             231        10    ______________________________________

                  TABLE 16    ______________________________________    Compositions of Examples 42 and 43 films.    (All Example films were quenched at    a temperature of 14° C.)           Layer A  Layer A   Layer C   Layer C    Example           PP       PP:PB     EVOH:EVA  EVOH:EVA    ______________________________________    42     3374     50/50     E105/EVA660                                        49:1    43     3374     50/50     E105/EVA660                                        19:1    ______________________________________

The tensile properties for each of the Example barrier films wereobtained as in Examples 1-4 and 6. Yield strain, fracture strain, yieldstress, fracture stress and Young's modulus for Examples 42-43 are givenin Table 17. At least three samples for each Example barrier film weremeasured for each value reported.

                  TABLE 17    ______________________________________    Yield strain, fracture strain, yield stress, fracture    stress and Young's modulus for Examples 42-43.           Yield    Fracture Yield  Fracture           Strain   Strain   Stress Stress Modulus    Example           (%)      (%)      (MPa)  (MPa)  (MPa)    ______________________________________    42     21       617      14     39     346    43     20       619      14     35     308    ______________________________________

Examples 42 and 43 illustrate that three-layer multilayered barrierfilms in accordance with the present invention can be formed by blendingEVA copolymer along with EVOH in the gas barrier layer of the presentinvention. When such a gas barrier layer is coextruded along with themesopolymer blends employed in the moisture barrier layer(s), amultilayered barrier film in accordance with the present invention canbe formed without the need to resort to optional adhesive layers.

EXAMPLE 44 AND COMPARISON EXAMPLE 45

Multilayered barrier films of sixty-five (65) layers were made on amultilayer coextrusion line utilizing three extruders. The 65-layeredconstruction consisted of opposing, outer moisture barrier layers(hereinafter layer "A"), each of which was followed by an adhesive layer(hereinafter layer "B"), and then a gas barrier layer (hereinafter layer"C"). Thereafter, the structure alternated layers as follows: layer B,layer A, layer B, layer C, layer B, layer A, layer B, layer C, etc.Layer A comprised polypropylene No. PP3014 (melt index=12 g/10 min.);Exxon, Inc.). Layer B comprised ADMER QF 551A (melt index=5.7 g/10 min.;Mitsui Plastics, Inc.). While, layer C comprised an EVOH copolymer, No.EVAL F101 (melt index=1.6 g/10 min.; Evalca Co.).

The Example and Comparison Example barrier films were cast on atemperature-controlled casting roll at a temperature of 81° C. forComparison Example 45, and 5° C. for Example 44. Wide-angle X-raydiffraction (WAXD) measurements of each of the films showed that theComparison Example 45 film contained undesirable crystallinepolypropylene of the isotactic I structure, while the quenched film ofExample 44 was of mesomorphous polypropylene structure. The films wereirradiated using electron-beam ionizing radiation and stored at roomtemperature for prolonged periods of time. The mechanical properties,including elongation to break, for the aging Example and Comparisonfilms, were measured utilizing an INSTRON Model 1122 machine accordingto ASTM D882-31, with a strain rate of 100% per minute. Table 18contains the percent elongation to break data for irradiated films ofExample 44 and Comparison Example 45 over time.

                                      TABLE 18    __________________________________________________________________________    Percent elongation to break data for irradiated    films of Example 44 and Comparison Example 45.    (Mon. = month; Q = quenched; NQ = nonquenched)    E-Beam     % Elong. to Break   Percent    Example         Dosage               Zero                   One  One                           Two Three                                   Retention    Number         (kGy) Week                   Week Mon.                           Mon.                               Mon.                                   (3 Mons.)    __________________________________________________________________________    Ex. 44          0    393 393  -- 386 380 97%    (Q)   50   393 321  338                           302 340 87%         100   393 317  338                           392 293 75%    Comp.          0    302 302  -- 363 350 116%    Ex. 45          50   302 268  204                            68  46 15%    (NQ) 100   302 178  150                            22  17  6%    __________________________________________________________________________

As the results in Table 16 illustrate, the quenched multilayered barrierfilm of Example 44, which contained mesomorphous polypropylene, retainedexcellent mechanical properties (i.e., percent elongation to break),even at three months after irradiation at 100 kGy (10 Mrad) dosages. Incontrast, the non-quenched, crystalline polypropylene containing film ofComparison Example 45 is nonfunctional three months after irradiation.

EXAMPLES 46-50, AND COMPARISON EXAMPLES 51-55

Multilayer barrier films corresponding in construction to Examples 1-4and 6, and Comparative Examples 5, and 7-10 (Example films 1-4 and 6were used for Examples 46-50; Comparison Example films 5 and 7-10 wereused for Comparison Examples 51-55) were electron beam irradiated at adosage of 50 kGy (5 Mrads) and then immediately placed in liquidnitrogen. Electron paramagnetic resonance (EPR) analysis was performedby first warming the films to room temperature, cutting them to 1.3cm×7.6 cm in size, weighing, and then mounting the film strips in tubes.This technique allows reproducible sample positioning in the EPR cavity.Radical peak heights were recorded for each sample as a function ofelapsed time from the initial measurement using a VARIAN model 4502spectrometer with a 23 cm magnet operating in the "X"-band. Fremy's saltwas used as the magnetic field reference. Peak height represents radicalconcentration as measured in spins/gram. Initial runs were used toestimate radical concentration, and the declining numbers areproportional to the initial number. Since different instrument settingswere used for some samples, all numbers were normalized. Spinconcentration was calibrated against the National Bureau of StandardsNo. 261 Ruby Standard.

Normalized radical peak height in spins/gram is shown in Table 19 as afunction of elapsed time (hours) for Examples 46-50 and ComparisonExamples 51-55. In all cases, radial decay occurs in the quenched films(Examples 46-50) at a much faster rate than in the comparisonnonquenched films (Comparison Examples 51-55). This is more clearlydemonstrated in FIGS. 18-20 where normalized radical peak height isplotted against elapsed time. For example, as FIG. 18 illustrates,radical decay occurs at consistently faster rate for the quenched filmof Example 46 (line A) in comparison to the nonquenched film ofComparison Example 52 (line B). Likewise, analogous results are shownwith the quenched film of Example 47 (line A) and Comparison Example 53(line B) in FIG. 19. Furthermore, excellent reproducibility of the datais demonstrated in FIG. 20 where values for quenched film Examples 48and 50 (line A) fall on the same general curve as for the nonquenchedfilms of Comparison Examples 54 (line B) and 55 (line C). Thus, thequenched films containing mesomorphous polypropylene are expected tomaintain their integrity and properties to a greater extent than theirnonquenched counterparts since the radicals available for degradationare reduced more rapidly in the quenched films than in the nonquenchedfilms.

                                      TABLE 19    __________________________________________________________________________    Normalized radical peak height in spins for grams as a function of    elapsed time in hours    after exposure of the multilayer barrier films of Examples 46-50 and    Comparison Examples    51-55 to electron beam radiation.    Elapsed                       Comp.                                       Comp.                                            Comp.                                                 Comp.                                                      Comp.    Time Example              Example                   Example                        Example                             Example                                  Example                                       Example                                            Example                                                 Example                                                      Example    (Hrs.)         No. 46              No. 47                   No.48                        No. 49                             No. 50                                  No. 51                                       No. 52                                            No. 53                                                 No. 54                                                      No. 55    __________________________________________________________________________     0   79   76   66   98   74   122  140  128  110  104     1   63   59   49   73   53   88   122  106  86   82     2   54   51   41   58   43   70   110  96   76   72     3   49   45   36   48   36   58   104  88   68   64    21   21   18   13   14   13   17   64   52   36   33    45   12   11   7    6.3  7    7    46   36   25   22    69   9    8    5    4    5    4    40   31   20   17    93   8    6    4    3    4    1    33   24   16   15    165  4    4    2    1    2    2    25   18   12   11    333  0.9  0.8  0.4  0.3  0.4  0.4  14   10    7    6    __________________________________________________________________________

EXAMPLES 56-71 AND COMPARISON EXAMPLES 72-84

Sixteen, five-layered coextruded barrier films were made using a flatfilm process as described in Examples 1-4 and 6 and, thirteen,five-layered coextruded barrier films were made as described forComparison Examples 5 and 7-10. The barrier films were generallycoextruded at a film thickness of about 75μ, with each moisture barrierlayer (hereinafter layer "A") being about 31μ thick, each adhesive layer(hereinafter layer "B") being about 4μ thick, and the gas barrier layer(hereinafter layer "C") being about 8μ thick. The construction of thefive-layer barrier films of Examples 56-71 and Comparison Examples 72-84corresponded to the multilayered constructions illustrated in FIG. 2herein.

Layer A comprised mixtures by weight of polypropylene resin (PP)(PP3576; melt index=9 g/10 min; Fina Oil and Chemical Co.) with ethylenevinyl acetate copolymer resin (EVA)(No. UE656; melt index=5.4 g/10 min.;12% vinyl acetate content; Quantum Chemical Corp.), or with ethyleneacrylic acid copolymer resin (EAA)(Primacor 3340; melt index=9 g/10min.; 6.5% acrylic acid comonomer content; Dow Chemical Co.), or withboth polybutylene resin (PB)(PB400; melt index=20 g/10 min.; ShellChemical Co.) and EVA, or with both PB and EAA. Layer B comprised apolypropylene based adhesive layer of resin sold under the trademark"ADMER QF 551 A" resin (melt index=5.7 g/10 min.); Mitsui Plastics,Inc.). Layer C was made of an ethylene vinyl alcohol copolymer(EVOH)(E105A, melt index=5.5 g/10 min.; Evalca Co.).

The blended mixtures were dry blended before being melted andcoextruded. The films for Examples 56-71 and Comparison Examples 72-84were extruded at a melt temperature of 221° C. for layer A, and 232° C.for layers B and C. Table 20 lists specific constructions for Examples56-71 and Comparison Examples 72-84. Temperature for the quench roll forExamples 56-71 was maintained at 10° C. in order to control themesomorphous structure of the polypropylene in the mesopolymer blend,while a quench temperature of 66° C. was utilized with ComparisonExamples 72-84, thereby resulting in crystalline polypropylene beingpresent in the polymer blends. Adhesive and gas barrier layerconstructions were kept constant across all the Examples and ComparisonExamples.

                  TABLE 20    ______________________________________    Film constructions and Young's Modulus values (MPa) for    Examples 56-71 and Comparison Examples 72-84.                                         Young's    Ex. No./                      Quench Modulus    Comp.              Blend Ratio                                  Temp.  Ex./Comp.    Ex. No.           Composition (Wt. %)    (°C.)                                         Ex.    ______________________________________    56/72  mPP:EVA     100/0      10/66  772/994    57/73  mPP:EVA     75/25      10/66  674/810    58/74  mPP:EVA     50/50      10/66  536/608    59/75  mPP:EVA     25/75      10/66  378/508    60/--  mPP:EVA     0/100      10/66  356/--    61/76  mPP:PB:EVA  50/50/0    10/66  482/618    62/77  mPP:PB:EVA  37.5/37.5/25                                  10/66  460/526    63/78  mPP:PB:EVA  25/25/50   10/66  346/454    64/79  mPP:PB:EVA  12.5/12.5/75                                  10/66  316/410    65/80  mPP:EAA     75/25      10/66  662/828    66/81  mPP:EAA     50/50      10/66  578/694    67/82  mPP:EAA     25/75      10/66  462/548    68/--  mPP:EAA     0/100      10/66  352/--    69/83  mPP:PB:EAA  37.5/37.5/25                                  10/66  480/582    70/84  mPP:PB:EAA  25/25/50   10/66  456/488    71/--  mPP:PB:EAA  12.5/12.5/75                                  10/66  384/--    ______________________________________

Tensile properties were performed on an INSTRON model 1122 machineaccording to the same procedures as disclosed in Examples 1-4 and 6, andComparison Examples 5 and 7-10 herein. In each case, at least threesamples of each Example and Comparison Example were measured for eachvalue reported.

The effect of the amount of mesomorphous polypropylene (mPP) in themoisture barrier layer (layer A) on the modulus (Young's modulus) forthe multilayered barrier films of Examples 56-71 (in comparison to theeffect of crystalline polypropylene in Comparison Examples 72-84 isshown in Table 20. In all cases, the modulus for the quenched films ofExamples 56-71 is 6.5%-41% lower than for the nonquenched films ofComparison Examples 72-84. A more detailed analysis for the effect ofmPP on barrier film modulus for Examples 56-60 is shown in FIG. 15. FormPP concentrations of less than about 70% (or EVA concentrations in themesopolymer blend of greater than 30%) the multilayered barrier filmsbecame less stiff (i.e., softer). As can be seen in FIG. 15, modulusvalues for the multilayered barrier films with mesopolymer blendconcentrations in this range (line A) (i.e., less than 70% mPP) arelower than would be expected from the Rule of Mixtures (line B), as thatterm is defined herein. Similar effects on modulus are shown in FIG. 16for the multilayered barrier films of Examples 60-64 with mPP:PB:EVAmesopolymer blend concentrations of less than about 70% of mPP and PB(or EVA concentrations in the mesopolymer blend greater than 30%). Aswith Examples 56-60, modulus values for the multilayered barrier filmswith mesopolymer blend concentrations in this range (line A) (i.e., lessthan 70% mPP:PB) are lower than would be expected from the Rule ofMixtures (line B). Thus, adding EVA to mPP or mPP:PB resins forming themoisture barrier layer of the multilayered barrier films synergisticallyresults in multilayered barrier films which are less stiff than would beexpected for mPP or mPP:PB mesopolymer blends in the concentration rangeof about 0% to 70%.

Synergy in fracture strain, as shown in FIG. 17, was also observed forExamples 61 and 68-71, where the moisture barrier, layer of themultilayered barrier films comprised a mesopolymer blend of mPP:PB:EAA.That is, fracture strains were greater than would be expected (line A)than under the Rule of Mixtures (line B), as that term is definedherein. Thus, using mPP:PB:EAA mesopolymer blends in the moisturebarrier layers of the multilayered barrier films results in films whichare surprisingly tougher (i.e., display a greater stain to fracture)than would be expected.

Oxygen transmission rate (O₂ TR) data was collected for the films ofExamples 58, 63, 66 and 70 according to the same procedures andutilizing the same equipment as described for Examples 1-4 and 6 herein.The results were normalized to a 25μ thick film, and reported in cc/m²/day-atmosphere at 25° C. and 0% relative humidity as per Examples 1-4and 6. The O₂ TR data for Examples 58, 63, 66 and 70 are reported inTable 21. The results indicate that mesopolymer blends of mesomorphouspolypropylene (mPP) and ethylene vinyl acetate (EVA) and ethyleneacrylic acid (EAA), either alone or in combination with polybutylene(PB), demonstrate comparable O₂ TR values to the mPP:PB compositionsreported in Table 6 herein.

                  TABLE 21    ______________________________________    Oxygen transmission rates (O.sub.2 TR) , as expressed in    cc/m.sup.2 /d-atm, for Examples 58, 63, 66, and 70.                                    O.sub.2 TR    Ex. No. Composition  Ratio (wt. %)                                    (cc/m.sup.2 /d-atm)    ______________________________________    58      mPP:EVA      50/50      3.3    63      mPP:PB:EVA   25/25/50   3.4    66      mPP:EAA      50/50      3.0    70      mPP:PB:EAA   25/25/50   3.0    ______________________________________

EXAMPLES 85-94

Five multilayered tubes and five multilayered pouches were formed fromthe multilayer barrier films of Examples 3, 58, 63, 66 and 70. To makethe tubes, the films were curved into a cylinder and heat sealed on oneedge using a heat sealer (sold under the trademark "SENTINEL" bySentinel Inc.). The pouches were made by either folding the Example filmover on itself, and then heat sealing two-sides, or by using two films,placing one on top of the other, and then heat sealing three of thesides. The tube and pouch dimensions, along with compositions of themoisture barrier layers of the films, are shown in Table 22 for thetubes of Examples 85-89, and in Table 23 for the pouches of Examples90-94.

                  TABLE 22    ______________________________________    Overall tube dimensions and composition of the    moisture barrier layers of the multilayered    tubings of Examples 85-89.            Original Moisture     Tube  Tube Wall    Example Example  Barrier Layer                                  Radius                                        Thickness    Number  Number   Composition  (cm)  (microns)    ______________________________________    85       3       PP:PB        1.9   102                     (50/50)    86      58       PP:EVA       1.3   74                     (50/50)    87      63       PP:PB:EVA    1.1   64                     (25/25/50)    88      66       PP:EAA       1.4   89                     (50/50)    89      70       PP:PBP:EAA   1.3   76                     (25/25/50)    ______________________________________

                  TABLE 23    ______________________________________    Overall pouch dimensions and composition of the moisture    barrier layers of the multilayered pouches    of Examples 90-94.                    Moisture           Original Barrier    Pouch Pouch Pouch    Example           Example  Layer      Length                                     Width Thickness    Number Number   Composition                               (cm)  (cm)  (microns)    ______________________________________    90      3       PP:PB      8     14    102                    (50/50)    91     58       PP:EVA     7     12    74                    (50/50)    92     63       PP:PB:EVA  6     11    64                    (25/25/50)    93     66       PP:EAA     8     11    89                    (50/50)    94     70       PP:PB:EAA  7     11    76                    (25/25/50)    ______________________________________

EXAMPLES 95-102, AND COMPARISON EXAMPLES 103-110

To determine noise generated by a film during wrinkling, an apparatuscapable of flexing a film sample in a cyclic and repeatable manner wasconstructed in accordance with the teaching of U.S. Pat. No. 4,376,799,the disclosure of which is herein incorporated by reference. Samples ofExample films were cut to 8.8 cm by 8.8 cm in size. One end of the filmwas wrapped around a stationary cylinder of 2.5 cm diameter and theother end to a second, rotatable cylinder displaced 5 cm parallel fromthe stationary cylinder. Thus, the film formed a cylinder whichconnected the stationary cylinder to the rotatable cylinder. Noise wasgenerated by the film when the motor was engaged and the rotatablecylinder and attached film were rotated 15° in a forward direction andthen 15° in the reverse direction at a frequency of 1.2 cycles persecond. A microphone inserted in the stationary cylinder was used topick up noise and generate an electrical signal which was used forfurther analysis. The signal from the microphone was processed through apreamplifier which measured sound level in decibels over a range of 0 to20 kHz. The signal was then routed to a frequency analyzer whichmeasured the intensity of generated sound in volts as a function of itsfrequency. These values were then recorded and used for noise dataanalysis. Background noise, that is, noise in the room as well as noisegenerated by the operating apparatus without an attached film, wassubtracted from the film noise spectrum to produce a spectrumcharacteristic of the film only. All tests were performed in an anechoicchamber.

Noise can be measured both in terms of its frequency and intensity. Ingeneral, sounds of high intensity and frequency seem louder to the humanear than sounds of lower intensity and frequency. Thus, a "quiet" filmshould exhibit a low frequency, low intensity noise spectrum. Noisespectra for quenched and nonquenched multilayer barrier films ofExamples 95-102 and Comparison Examples 103-110 were generated. Noisedata for both quenched films and the corresponding nonquenched films areshown in FIGS. 21-36. Table 24 correlates the FIG. number with theExample and Comparison Example number, casting roll temperature and filmcomposition. In all cases, the quenched multilayer barrier films arequieter than the nonquenched films of the same, but nonquenched,composition.

                  TABLE 24    ______________________________________    Film constructions and correlation to FIG. No. for films    of Examples 95-102 and Comparison Examples 103-110    (EN = Example Number; CEN = Comparison Example    Number; ON = Original Example Number; OCN = Original    Comparison Example Number).                           Casting                           Roll  Moisture Component    EN/    ON/     FIG.    Temp. Layer    Weight    CEN    OCN     No.     (°C.)                                 Comp.    Ratio    ______________________________________     95/103           1/7     21/22   10/66 PP:PB    100:0     96/104           2/8     23/24   10/66 PP:PB    80:20     97/105           6/9     25/26   10/66 PP:PB    50:50     98/106           57/73   27/28   10/66 PP:EVA   75:25     99/107           63/78   29/30   10/66 PP:PB:EVA                                          25:25:50    100/108           64/79   31/32   10/66 PP:PB:EVA                                          12.5:12.5:75    101/109           66/81   33/34   10/66 PP:EAA   50:50    102/110           69/84   35/36   10/66 PP:PB:EAA                                          37.5:37.5:25    ______________________________________

EXAMPLES 111-114 AND COMPARATIVE EXAMPLES 115-118

Films of the present invention may desirably have an additional layergrafted to the film to enhance other properties such as surfaceadhesion, permeability, coefficient of friction, or other propertiesdesirable to those skilled in the art for the film. For example, not byway of limitation, surface adhesion is desirable in order to provide theapplication of primers and other coatings to a film that would nototherwise adhere well to a film of the present invention.

Using methods identified in European Patent Publication EPO 0297741, thesurface adhesion layer is desirably grafted to the films of the presentinvention by electron beam irradiation in dosages of from about 0.5 Mrad(5 kGy) to about 20 Mrad (200 kGy) and preferably about 5 Mrad (50 kGy).The compounds desirably to be grafted to the polymer blend film includeacrylic acid (AA), dimethylacrylamide (DMA), N-vinyl-2-pyrrolidone(NVP), and a copolymer of NVP and trimethylolpropanetriacrylate(NVP/TMPTA). Other possible compounds to be used as a grafting layerinclude glycidyl acrylate, hydroxethyl acrylate, hydroxymethyl acrylate,2-vinyl pyridine, sulfoethyl methacrylate, eliisopropylacrylamide, orN,N-diethylamino acrylate.

Exemplary compounds could be grafted onto films prepared in the samemanner as that for films of Example 3 and Comparative Example 9.Grafting could use electron beam generating dosages identified in Table25 in a nitrogen atmosphere at 175 kv with a web speed of 25 feet perminute (7.62 m/min).

The strength of the graft could be measured using a 180° peel adhesiontest described as follows: A 2.5 cm wide, 20.3 cm long strip ofpressure-sensitive adhesive tape (SCOTCH brand tape no. 8411) is adheredto a 10.1 cm wide, 15.2 cm long sheet of test substrate with a free endof the tape extending beyond the end of the test substrate. The sampleis rolled twice with a 1.35 kg hard rubber roller to ensure contactbetween the adhesive and the test substrate. The sample is aged at roomtemperature (22° C.) for 24 hours. The free end of the tape is removedfrom the test substrate at a rate of 6 inches/minute (15.24 cm/min)using a Slip/Peel Tester, available from Instrumentors, Inc.

                  TABLE 25    ______________________________________    Electron Beam Conditions for Radiation Graft    Modified Films of the Invention    Example    Grafted Monomer                            e-Beam Irradiation (kGy)    ______________________________________    Ex. 111    AA            50    Ex. 112    DMA           50    Ex. 113    NVP          100    Ex. 114    NVP/TMPTA    100    Comp. Ex. 115               AA            50    Comp. Ex. 116               DMA           50    Comp. Ex. 117               NVP          100    Comp. Ex. 118               NVP/TMPTA    100    ______________________________________

The grafted films of Example 111-114 would be expected to have improvedsurface adhesion as would the films of Comparative Examples 115-118.However, it would be expected that the grafted films of the presentinvention would not lose structural integrity, whereas the films ofComparative Examples 115-118 would degrade.

While in accordance with the patent statutes, description of thepreferred weight fractions, processing conditions, and product usageshave been provided, the scope of the invention is not to be limitedthereto or thereby. Various modifications and alterations of the presentinvention will be apparent to those skilled in the art without departingfrom the scope and spirit of the present invention. The examplesdescribed in this application are illustrative of the possibilities ofvarying the amounts and types of polymeric materials in the multilayeredbarrier structures to achieve properties for specific purposes.

Consequently, for an understanding of the scope of the presentinvention, reference is made to the following claims.

What is claimed is:
 1. A multilayered structure comprising:(a) a gasbarrier layer having opposing sides, and comprising a non-chlorinecontaining organic polymer which is substantially impermeable to oxygengas; and (b) at least one moisture barrier layer comprising a mesophasepropylene-based material contacting at least one of the sides of the gasbarrier layer.
 2. A multilayered structure according to claim 1, whereinthe non-chlorine containing organic polymer is avinyl-alcohol-containing polymer.
 3. A multilayered structure accordingto claim 2, wherein the vinyl-alcohol-containing polymer is selectedfrom the group consisting of ethylene vinyl alcohol copolymer,poly(vinyl alcohol) copolymer, and combinations thereof.
 4. Amultilayered structure according to claim 1, wherein the non-chlorinecontaining organic polymer is selected from the group consisting ofpolyacrylonitrile, polystyrene, polyester, nylon, and combinationsthereof.
 5. A multilayered structure according to claim 1, wherein thenon-chlorine containing organic polymer exhibits a permeability tooxygen gas of less than about 100 cc/m² /d-atm at 25° C. and 0% relativehumidity.
 6. A multilayered structure according to claim 1 wherein thenon-chlorine containing organic polymer exhibits a permeability tooxygen gas of less than about 30 cc/m² /d-atm at 25° C. and 0% relativehumidity.
 7. A multilayered structure according to claim 1 wherein thenon-chlorine containing organic polymer exhibits a permeability tooxygen gas of less than about 5 cc/m² /d-atm at 25° C. and 0% relativehumidity.
 8. A multilayered structure according to claim 1, wherein themesophase propylene-based material is selected from the group consistingof mesomorphous polypropylene, a mesopolymer blend, a mesocopolymer, andcombinations thereof.
 9. A multilayered structure according to claim 8,wherein the mesopolymer blend comprises a blend of mesomorphouspolypropylene and at least a discernable amount of a second polymer. 10.A multilayered structure according to claim 9, wherein the secondpolymer is selected from the group consisting of polybutylene, ethylenevinyl acetate copolymer, ethylene acrylic acid copolymer, andcombinations thereof.
 11. A multilayered structure according to claim 9,wherein the second polymer of the mesopolymer blend is compatible withmesomorphous polypropylene.
 12. A multilayered structure according toclaim 11, wherein the compatible second polymer is polybutylene and thenon-chlorine containing organic polymer is ethylene vinyl alcoholcopolymer.
 13. A multilayered structure according to claim 11, whereinthe multilayered structure exhibits a synergistic enhancement of atleast one physical property of the multilayered barrier structure betterthan what would be expected under the Rule of Mixtures.
 14. Amultilayered structure according to claim 13, wherein the multilayeredstructure exhibits a synergistic enhancement in Young's modulus, yieldstress, fracture strain, or frequency of noise emitted in Hertz.
 15. Amultilayered structure according to claim 9, wherein the amount of thesecond polymer is from about twentyfive percent to about seventy-fivepercent by weight of the mesopolymer blend.
 16. A multilayered structureaccording to claim 9, wherein the amount of the second polymer is fromabout forty percent to about sixty percent by weight of the mesopolymerblend.
 17. A multilayered structure according to claim 9, wherein theamount of the second polymer is from about one percent to aboutninety-nine percent by weight of the mesopolymer blend.
 18. Amultilayered structure according to claim 9, wherein the amount of thesecond polymer is from about ten percent to about ninety percent byweight of the mesopolymer blend.
 19. A multilayered structure accordingto claim 9, wherein the second polymer of the mesopolymer blendcomprises about ninety percent by weight of ethylene vinyl acetate, thesecond polymer being blended with about ten percent by weight ofmesomorphous polypropylene.
 20. A multilayered structure according toclaim 9, wherein the second polymers of the mesopolymer blend comprisesabout seventy-six percent by weight of ethylene vinyl acetate and twelvepercent by weight of polybutylene, the second polymers being blendedwith about twelve percent by weight of mesomorphous polypropylene.
 21. Amultilayered structure according to claim 8, wherein the mesocopolymercomprises a propylene-based material with a discernable amount of atleast one moiety.
 22. A multilayered structure according to claim 21,wherein the moiety is selected from the group consisting of a molecule,a monomer, a polymer, and combinations thereof.
 23. A multilayeredstructure according to claim 22, wherein the molecule is selected fromthe group consisting of an acid molecule, an anhydride molecule, anacid-anhydride molecule, an acetate molecule, an acrylate molecule, andcombinations thereof.
 24. A multilayered structure according to claim22, wherein the monomer is selected from the group consisting ofethylene, butylene, pentene, methylpentene, and combinations thereof.25. A multilayered structure according to claim 21, wherein thepropylene-based material of the mesocopolymer comprises from about onepercent to about ninety nine percent by weight of the mesocopolymer. 26.A multilayered structure according to claim 21, wherein thepropylene-based material of the mesocopolymer comprises from aboutninety percent to about ninety nine percent by weight of themesocopolymer.
 27. A multilayered structure according to claim 21,wherein the propylene-based material comprises propylene monomer at fromabout ninety percent to about ninety nine percent by weight of themesocopolymer, and the moiety comprises ethylene monomer at from aboutten percent to about one percent by weight of the mesocopolymer.
 28. Amultilayered structure according to claim 27, wherein the ionizingradiation comprises gamma radiation or electron-beam radiation.
 29. Amultilayered structure according to claim 1, wherein the structure iscapable of substantially maintaining its structural integrity for auseful period of time after exposure to a dosage of ionizing radiationof from about 1 kGy to about 100 kGy.
 30. A multilayered structureaccording to claim 1, wherein the structure is heat-sealable to itselfor to other heat-sealable materials.
 31. A multilayered structureaccording to claim 1, wherein the multilayered structure furthercomprises one or more adhesive layers disposed between the gas barrierlayer and moisture barrier layer.
 32. A multilayered structure accordingto claim 31, wherein the adhesive layer comprises a functionalizedolefin polymer or polymer blend.
 33. A multilayered structure accordingto claim 32, wherein the functionalized olefin polymer is selected fromthe group consisting of an anhydride of a polyolefin, an acid of apolyolefin, an acid/anhydride of a polyolefin, and combinations thereof.34. A multilayered structure according to claim 31, wherein the adhesivelayer comprises a functionalized mesocopolymer.
 35. A multilayeredstructure according to claim 34, wherein the adhesive layer comprisesthe moisture barrier layer of the multilayered structure.
 36. Amultilayered structure according to claim 1, wherein the gas barrierlayer and moisture barrier layer are coextruded.
 37. A multilayeredstructure according to claim 36, wherein the gas barrier layer andmoisture barrier layer are coextruded as a multilayered film or tube.38. A multilayered structure according to claim 36, wherein thecoextruded multilayered structure is assembled into an ostomy pouch. 39.A multilayered structure according to claim 1, wherein the multilayeredstructure further comprises a fabric backing affixed to at least aportion of the multilayered structure.
 40. A multilayered structureaccording to claim 39, wherein the fabric backing is selected from thegroup consisting of a woven material, a nonwoven material, andcombinations thereof.
 41. A multilayered structure according to claim40, wherein the nonwoven material comprises a web of melt blownmicrofibers.
 42. A multilayered structure according to claim 39, whereinthe multilayered structure is assembled into an ostomy pouch, andwherein the fabric backing provides a comfortable surface for contactingthe skin of a wearer of the ostomy pouch.
 43. A radiation resistantarticle formed from a multilayered structure comprising:(a) a gasbarrier layer having opposing sides, and comprising a non-chlorinecontaining organic polymer which is substantially impermeable to oxygengas; and (b) at least one moisture barrier layer comprising a mesophasepropylene-based material contacting at least one of the sides of the gasbarrier layer, wherein the article is quenched immediately after beingmelt extruded.
 44. A radiation resistant article according to claim 43,wherein the article comprises a film, a fiber, a microfiber, a tube, ora pouch.
 45. A multilayered structure comprising:a gas barrier layerhaving opposing sides, and comprising a non-chlorine containing organicpolymer selected from the group consisting of ethylene vinyl alcoholcopolymer, poly(vinyl alcohol) copolymer, polyacrylonitrile,polystyrene, polyester, nylon, and combinations thereof, wherein thenon-chlorine containing organic polymer exhibits a permeability tooxygen gas of less than about 150 cc/m² /d-atm at 25° C. and 0% relativehumidity; and at least one moisture barrier layer comprising a mesophasepropylene-based material selected from the group consisting ofmesomorphous polypropylene, a mesopolymer blend, a mesocopolymer, andcombinations thereof, contacting at least one of the sides of the gasbarrier layer.
 46. A multilayered structure according to claim 45,wherein the structure is capable of substantially maintaining itsstructural integrity for a useful period of time after exposure to adosage of ionizing radiation of from about 1 kGy to about 100 kGy.
 47. Amultilayered structure according to claim 45, wherein the mesopolymerblend comprises a blend of mesomorphous polypropylene and at least adiscernible amount of a second polymer selected from the groupconsisting of polybutylene, ethylene vinyl acetate copolymer, ethyleneacrylic acid copolymer, and combinations thereof.
 48. A multilayeredstructure according to claim 45, wherein the structure is heat-sealableto itself or to other heat-sealable materials.
 49. A multilayeredstructure according to claim 45, wherein the gas barrier layer andmoisture barrier layer are coextruded.
 50. A multilayered structureaccording to claim 49, wherein the gas barrier layer and moisturebarrier layer are coextruded as a multilayered film or tube.
 51. Amultilayered structure according to claim 49, wherein the coextrudedmultilayered structure is assembled into an ostomy pouch.
 52. Amultilayered structure according to claim 45, wherein the multilayeredstructure further comprises a fabric backing selected from the groupconsisting of a woven material, a nonwoven material, and combinationsthereof, affixed to at least a portion of the multilayered structure.53. A multilayered structure according to claim 52, wherein themultilayered structure is assembled into an ostomy pouch, and whereinthe fabric backing provides a comfortable surface for contacting theskin of a wearer of the ostomy pouch.
 54. A multilayered structurecomprising:a gas barrier layer having opposing sides, and comprising anon-chlorine containing organic polymer selected from the groupconsisting of ethylene vinyl alcohol copolymer, poly(vinyl alcohol)copolymer, polyacrylonitrile, polystyrene, polyester, nylon, andcombinations thereof, wherein the non-chlorine containing organicpolymer exhibits a permeability to oxygen gas of less than about 100cc/m² /d-atm at 25° C. and 0% relative humidity; and at least onemoisture barrier layer comprising a mesophase propylene-based materialselected from the group consisting of mesomorphous polypropylene, amesopolymer blend, a mesocopolymer, and combinations thereof, whereinthe gas barrier layer and moisture barrier layer are coextruded as amultilayered film or tube.
 55. A multilayered structure according toclaim 54, wherein the multilayered structure further comprises a fabricbacking selected from the group consisting of a woven material, anonwoven material, and combinations thereof, affixed to at least aportion of the multilayered structure, wherein the multilayeredstructure is assembled into an ostomy pouch, and wherein the fabricbacking provides a comfortable surface for contacting the skin of awearer of the ostomy pouch.